> today i accidentally nuked everything by not flushing the disk before rebooting
What do you mean? Did you interrupt the reboot process (eg. repetitive ^C)? Otherwise the OS should flush everything properly.
> after this i have to figure out a better backup solution
If you have other friends doing selfhosting, giving them a HDD to put in their server so you can rsync your data is a good solution. Also, keeping another local backup is a good solution. Doing both is even better.
> AFAICT it’s pretty much impossible to 100% self-host email because of blacklisting
It depends. It's almost impossible with some bad-faith providers (google/microsoft) otherwise everything works well. And even with those bad-faith providers, residential IPs usually have better reputation (if only because your ISP likely blocks outgoing TCP 25 by default and you have to ask them to unfilter it) than VPS IPs which all have a long history of abuse.
> and in between that i may spin up a DNS server to overcome the part where it takes 60min for any new service to be accessible
If you didn't previously query that domain name on your resolver, it will not be cached and will resolve quasi-instantly. The question is how long does your authoritative name server take to apply your changes to the config: if it takes any longer than 10s you should consider switching providers.
> but maybe we can federate, so that you just need to have one friend who cares about this stuff manage the infra and provide it to their peers as a social good.
Very good point! That's the entire premise behind hosting coops like disroot.org or various members of the libreho.st/chatons.org federations.