Any chance of supporting NameCheap for the DNS service? They're very privacy friendly and better yet, their DNS service is free even if you don't have any domains registered with them (I use them for a domain I have with Internetbs.com )
As far as I can see, all of the currently supported options are either privacy holes (Google) or require you to pay them in one way or another to be able to use their DNS service...
By the way, the links to DNS services on https://www.cloudron.io/documentation/installation/ seem to be broken.