In case Cloudron team decides to implement this, I just noticed that MainWP is creating an extension for this, and they seem to document all their sources for the various WHOIS data for each TLD they support here: https://kb.mainwp.com/docs/mainwp-domain-monitor-extension/
Anyone who has MainWP... feel free to use that extension too in the meantime.
In case the sources go away later, here it is for posterity sake:
"ac" => "whois.nic.ac", // Ascension Island.
// ad - Andorra - no whois server assigned.
"ae" => "whois.nic.ae", // United Arab Emirates.
"aero"=>"whois.aero",
"af" => "whois.nic.af", // Afghanistan.
"ag" => "whois.nic.ag", // Antigua And Barbuda.
"ai" => "whois.ai", // Anguilla.
"al" => "whois.ripe.net", // Albania.
"am" => "whois.amnic.net", // Armenia.
// an - Netherlands Antilles - no whois server assigned.
// ao - Angola - no whois server assigned.
// aq - Antarctica (New Zealand) - no whois server assigned.
// ar - Argentina - no whois server assigned.
"arpa" => "whois.iana.org",
"as" => "whois.nic.as", // American Samoa.
"asia" => "whois.nic.asia",
"at" => "whois.nic.at", // Austria.
"au" => "whois.aunic.net", // Australia.
// aw - Aruba - no whois server assigned.
"ax" => "whois.ax", // Aland Islands.
"az" => "whois.ripe.net", // Azerbaijan.
// ba - Bosnia And Herzegovina - no whois server assigned.
// bb - Barbados - no whois server assigned.
// bd - Bangladesh - no whois server assigned.
"be" => "whois.dns.be", // Belgium.
"bg" => "whois.register.bg", // Bulgaria.
"bi" => "whois.nic.bi", // Burundi.
"biz" => "whois.biz",
"bj" => "whois.nic.bj", // Benin.
// bm - Bermuda - no whois server assigned.
"bn" => "whois.bn", // Brunei Darussalam.
"bo" => "whois.nic.bo", // Bolivia.
"br" => "whois.registro.br", // Brazil.
"bt" => "whois.netnames.net", // Bhutan.
// bv - Bouvet Island (Norway) - no whois server assigned.
// bw - Botswana - no whois server assigned.
"by" => "whois.cctld.by", // Belarus.
"bz" => "whois.belizenic.bz", // Belize.
"ca" => "whois.cira.ca", // Canada.
"cat" => "whois.cat", // Spain.
"cc" => "whois.nic.cc", // Cocos (Keeling) Islands.
"cd" => "whois.nic.cd", // Congo, The Democratic Republic Of The.
// cf - Central African Republic - no whois server assigned.
"ch" => "whois.nic.ch", // Switzerland.
"ci" => "whois.nic.ci", // Cote d'Ivoire.
"ck" => "whois.nic.ck", // Cook Islands.
"cl" => "whois.nic.cl", // Chile.
// cm - Cameroon - no whois server assigned.
"cn" => "whois.cnnic.net.cn", // China.
"co" => "whois.nic.co", // Colombia.
"com" => "whois.verisign-grs.com",
"coop" => "whois.nic.coop",
// cr - Costa Rica - no whois server assigned.
// cu - Cuba - no whois server assigned.
// cv - Cape Verde - no whois server assigned.
// cw - Curacao - no whois server assigned.
"cx" => "whois.nic.cx", // Christmas Island.
// cy - Cyprus - no whois server assigned.
"cz" => "whois.nic.cz", // Czech Republic.
"de" => "whois.denic.de", // Germany.
// dj - Djibouti - no whois server assigned.
"dk" => "whois.dk-hostmaster.dk", // Denmark.
"dm" => "whois.nic.dm", // Dominica.
// do - Dominican Republic - no whois server assigned.
"dz" => "whois.nic.dz", // Algeria.
"ec" => "whois.nic.ec", // Ecuador.
"edu" => "whois.educause.edu",
"ee" => "whois.eenet.ee", // Estonia.
"eg" => "whois.ripe.net", // Egypt.
// er - Eritrea - no whois server assigned.
"es" => "whois.nic.es", // Spain.
// et - Ethiopia - no whois server assigned.
"eu" => "whois.eu",
"fi" => "whois.ficora.fi", // Finland.
// fj - Fiji - no whois server assigned.
// fk - Falkland Islands - no whois server assigned.
// fm - Micronesia, Federated States Of - no whois server assigned.
"fo" => "whois.nic.fo", // Faroe Islands.
"fr" => "whois.nic.fr", // France.
// ga - Gabon - no whois server assigned.
"gd" => "whois.nic.gd", // Grenada.
// ge - Georgia - no whois server assigned.
// gf - French Guiana - no whois server assigned.
"gg" => "whois.gg", // Guernsey.
// gh - Ghana - no whois server assigned.
"gi" => "whois2.afilias-grs.net", // Gibraltar.
"gl" => "whois.nic.gl", // Greenland (Denmark).
// gm - Gambia - no whois server assigned.
// gn - Guinea - no whois server assigned.
"gov" => "whois.nic.gov",
// gr - Greece - no whois server assigned.
// gt - Guatemala - no whois server assigned.
"gs" => "whois.nic.gs", // South Georgia And The South Sandwich Islands.
// gu - Guam - no whois server assigned.
// gw - Guinea-bissau - no whois server assigned.
"gy" => "whois.registry.gy", // Guyana.
"hk" => "whois.hkirc.hk", // Hong Kong.
// hm - Heard and McDonald Islands (Australia) - no whois server assigned.
"hn" => "whois.nic.hn", // Honduras.
"hr" => "whois.dns.hr", // Croatia.
"ht" => "whois.nic.ht", // Haiti.
"hu" => "whois.nic.hu", // Hungary.
// id - Indonesia - no whois server assigned.
"ie" => "whois.domainregistry.ie", // Ireland.
"il" => "whois.isoc.org.il", // Israel.
"im" => "whois.nic.im", // Isle of Man.
"in" => "whois.inregistry.net", // India.
"info" => "whois.afilias.net",
"int" => "whois.iana.org",
"io" => "whois.nic.io", // British Indian Ocean Territory.
"iq" => "whois.cmc.iq", // Iraq.
"ir" => "whois.nic.ir", // Iran, Islamic Republic Of.
"is" => "whois.isnic.is", // Iceland.
"it" => "whois.nic.it", // Italy.
"je" => "whois.je", // Jersey.
// jm - Jamaica - no whois server assigned.
// jo - Jordan - no whois server assigned.
"jobs" => "jobswhois.verisign-grs.com",
"jp" => "whois.jprs.jp", // Japan.
"ke" => "whois.kenic.or.ke", // Kenya.
"kg" => "www.domain.kg", // Kyrgyzstan.
// kh - Cambodia - no whois server assigned.
"ki" => "whois.nic.ki", // Kiribati.
// km - Comoros - no whois server assigned.
// kn - Saint Kitts And Nevis - no whois server assigned.
// kp - Korea, Democratic People's Republic Of - no whois server assigned.
"kr" => "whois.kr", // Korea, Republic Of.
// kw - Kuwait - no whois server assigned.
// ky - Cayman Islands - no whois server assigned.
"kz" => "whois.nic.kz", // Kazakhstan.
"la" => "whois.nic.la", // Lao People's Democratic Republic.
// lb - Lebanon - no whois server assigned.
// lc - Saint Lucia - no whois server assigned.
"li" => "whois.nic.li", // Liechtenstein.
// lk - Sri Lanka - no whois server assigned.
"lt" => "whois.domreg.lt", // Lithuania.
"lu" => "whois.dns.lu", // Luxembourg.
"lv" => "whois.nic.lv", // Latvia.
"ly" => "whois.nic.ly", // Libya.
"ma" => "whois.iam.net.ma", // Morocco.
// mc - Monaco - no whois server assigned.
"md" => "whois.nic.md", // Moldova.
"me" => "whois.nic.me", // Montenegro.
"mg" => "whois.nic.mg", // Madagascar.
// mh - Marshall Islands - no whois server assigned.
"mil" => "whois.nic.mil",
// mk - Macedonia, The Former Yugoslav Republic Of - no whois server assigned.
"ml" => "whois.dot.ml", // Mali.
// mm - Myanmar - no whois server assigned.
"mn" => "whois.nic.mn", // Mongolia.
"mo" => "whois.monic.mo", // Macao.
"mobi" => "whois.dotmobiregistry.net",
"mp" => "whois.nic.mp", // Northern Mariana Islands.
// mq - Martinique (France) - no whois server assigned.
// mr - Mauritania - no whois server assigned.
"ms" => "whois.nic.ms", // Montserrat.
// mt - Malta - no whois server assigned.
"mu" => "whois.nic.mu", // Mauritius.
"museum" => "whois.museum",
// mv - Maldives - no whois server assigned.
// mw - Malawi - no whois server assigned.
"mx" => "whois.mx", // Mexico.
"my" => "whois.domainregistry.my", // Malaysia.
// mz - Mozambique - no whois server assigned.
"na" => "whois.na-nic.com.na", // Namibia.
"name" => "whois.nic.name",
"nc" => "whois.nc", // New Caledonia.
// ne - Niger - no whois server assigned.
"net" => "whois.verisign-grs.net",
"nf" => "whois.nic.nf", // Norfolk Island.
"ng" => "whois.nic.net.ng", // Nigeria.
// ni - Nicaragua - no whois server assigned.
"nl" => "whois.domain-registry.nl", // Netherlands.
"no" => "whois.norid.no", // Norway.
// np - Nepal - no whois server assigned.
// nr - Nauru - no whois server assigned.
"nu" => "whois.nic.nu", // Niue.
"nz" => "whois.srs.net.nz", // New Zealand.
"om" => "whois.registry.om", // Oman.
"org" => "whois.pir.org",
// pa - Panama - no whois server assigned.
"pe" => "kero.yachay.pe", // Peru.
"pf" => "whois.registry.pf", // French Polynesia.
// pg - Papua New Guinea - no whois server assigned.
// ph - Philippines - no whois server assigned.
// pk - Pakistan - no whois server assigned.
"pl" => "whois.dns.pl", // Poland.
"pm" => "whois.nic.pm", // Saint Pierre and Miquelon (France).
// pn - Pitcairn (New Zealand) - no whois server assigned.
"post" => "whois.dotpostregistry.net",
"pr" => "whois.nic.pr", // Puerto Rico.
"pro" => "whois.dotproregistry.net",
// ps - Palestine, State of - no whois server assigned.
"pt" => "whois.dns.pt", // Portugal.
"pw" => "whois.nic.pw", // Palau.
// py - Paraguay - no whois server assigned.
"qa" => "whois.registry.qa", // Qatar.
"re" => "whois.nic.re", // Reunion (France).
"ro" => "whois.rotld.ro", // Romania.
"rs" => "whois.rnids.rs", // Serbia.
"ru" => "whois.tcinet.ru", // Russian Federation.
// rw - Rwanda - no whois server assigned.
"sa" => "whois.nic.net.sa", // Saudi Arabia.
"sb" => "whois.nic.net.sb", // Solomon Islands.
"sc" => "whois2.afilias-grs.net", // Seychelles.
// sd - Sudan - no whois server assigned.
"se" => "whois.iis.se", // Sweden.
"sg" => "whois.sgnic.sg", // Singapore.
"sh" => "whois.nic.sh", // Saint Helena.
"si" => "whois.arnes.si", // Slovenia.
"sk" => "whois.sk-nic.sk", // Slovakia.
// sl - Sierra Leone - no whois server assigned.
"sm" => "whois.nic.sm", // San Marino.
"sn" => "whois.nic.sn", // Senegal.
"so" => "whois.nic.so", // Somalia.
// sr - Suriname - no whois server assigned.
"st" => "whois.nic.st", // Sao Tome And Principe.
"su" => "whois.tcinet.ru", // Russian Federation.
// sv - El Salvador - no whois server assigned.
"sx" => "whois.sx", // Sint Maarten (dutch Part).
"sy" => "whois.tld.sy", // Syrian Arab Republic.
// sz - Swaziland - no whois server assigned.
"tc" => "whois.meridiantld.net", // Turks And Caicos Islands.
// td - Chad - no whois server assigned.
"tel" => "whois.nic.tel",
"tf" => "whois.nic.tf", // French Southern Territories.
// tg - Togo - no whois server assigned.
"th" => "whois.thnic.co.th", // Thailand.
"tj" => "whois.nic.tj", // Tajikistan.
"tk" => "whois.dot.tk", // Tokelau.
"tl" => "whois.nic.tl", // Timor-leste.
"tm" => "whois.nic.tm", // Turkmenistan.
"tn" => "whois.ati.tn", // Tunisia.
"to" => "whois.tonic.to", // Tonga.
"tp" => "whois.nic.tl", // Timor-leste.
"tr" => "whois.nic.tr", // Turkey.
"travel" => "whois.nic.travel",
// tt - Trinidad And Tobago - no whois server assigned.
"tv" => "tvwhois.verisign-grs.com", // Tuvalu.
"tw" => "whois.twnic.net.tw", // Taiwan.
"tz" => "whois.tznic.or.tz", // Tanzania, United Republic Of.
"ua" => "whois.ua", // Ukraine.
"ug" => "whois.co.ug", // Uganda.
"uk" => "whois.nic.uk", // United Kingdom.
"us" => "whois.nic.us", // United States.
"uy" => "whois.nic.org.uy", // Uruguay.
"uz" => "whois.cctld.uz", // Uzbekistan.
// va - Holy See (vatican City State) - no whois server assigned.
"vc" => "whois2.afilias-grs.net", // Saint Vincent And The Grenadines.
"ve" => "whois.nic.ve", // Venezuela.
"vg" => "whois.adamsnames.tc", // Virgin Islands, British.
// vi - Virgin Islands, US - no whois server assigned.
// vn - Viet Nam - no whois server assigned.
// vu - Vanuatu - no whois server assigned.
"wf" => "whois.nic.wf", // Wallis and Futuna.
"ws" => "whois.website.ws", // Samoa.
"xxx" => "whois.nic.xxx",
// ye - Yemen - no whois server assigned.
"yt" => "whois.nic.yt", // Mayotte.
"yu" => "whois.ripe.net"