@rosano 2GB is the minimum for a single Discourse app, if you have other apps running as well, it's probably not enough - so yes, more RAM = better. I haven't tried a migration, but installing and setting it up worked fine.
Yikes I had made numerous mistakes and it is working now. I had changed my username from admin and I was including the ruby prompts in the commands. I'm still brand new to Cloudron so hopefully I will have less and better questions in the future. Thanks so much @girish
I changed the version to "stable", so there were no downgrade (2.6.0beta7 ->>2.6.0).
rest is simple, (here is steps for anyone who want to migrate)
just install discourse on cloudron,
set a demo subdomain to avoid (down time),
upload backup file, start restoring process.
once restore completed u will logout, signin again with your admin account (The one you use on migrated).
go to cloudron dashboard & change to to the real domain. update it from domain register if you use manual domain.
be sure in discourse dashboard that the notification email domain is OK.
it will take around 1 minute with almost zero down time.
to be sure everything is OK, shut down the old server/vps.
I finally tested on a fresh install... and it works. So I dug some more, comparing the two installations, and realized at some point is a JS error on my regular install, linked to the chat integration plugin. In the end the code was outdated (it relied on a deprecated API), so I pulled the last version from git and... it worked.
Long story short: this was a plugin bug 🤷 Sorry for the noise, and thanks for suggesting testing a separate install!
Great - adding the subdomain in Cloudron and setting up Amazon SES login for that fixed the issue so I can now both send (via SES) and receive emails (via a Zoho pop mail box), including reply by email mode.
Thanks for your advice everyone!