Don’t over think it, start small, a home server. Then add stuff, you will see that it’s not that crazy.

I personally have just one home server that locally creates encrypted backups and uploads them to backblaze.

This gives me the privacy I need as everything is on my server that I own while also having the backups on a big reliable company.

It’s not perfect but it fits my threat model

All of your issues can be solved by a backup. My host went out of business. I set up a new server, pulled my backups, and was up and running in less than an hour.

I’d recommend docker compose. Each service gets its own folder inside your docker folder. All volumes are a folder in the services folder. Each night, run a script that stops all of them, starts duplicati, backs up to a remote server or webdav share or whatever, and then starts them back up again. If you want to be extra safe, back up to two locations. It’s not that complicated if it’s just your own services.

TrueNAS scale helps a lot, as it makes many popular apps just a few clicks away. Or for more power-users, stuff like the linux cockpit also really helps.

To directly answer your questions…

• In the event of DB corruption (which hasn’t happened to me yet) I would probably rollback that app to the previous snapshot. I suspect that TrueNAS having ZFS as an underlayment may help in this regard, as it actually detects bitrot and bitflips, which may be the underlying cause of such corruption.
• In the case where a device breaks… if it’s a hard drive that broke, I just pop in a new one and add it to the degraded mirror set. If it’s “something else” that broke, my plan is to pop one of the mirror shards into a spare PoS computer (as truenas scale runs on common x86 hardware) and deal with the ugly-factor until I repair or replace the bigger issue.
• The only way to defend against a cloud provider is replication, so plan accordingly if that is a concern.
• If by “sync’d confidentially” you mean encrypted in transit, I’m pretty sure that TrueNAS has built in replication over SSH. If you meant TNO, then you probably want to build your setup over a cryfs filesystem so no cleartext bits hit the cloud, although on second thought… it’s not really meant for multi-master synchronization… my case just happens to fit it (only one device writes)… so there is probably a better choice for this.
• Setup is a hassle? Yes… just be sure that you invest that hassle into something permanent, if not something like a TrueNAS configuration (where the config gets carried along for the ride with the data) then maybe something like ansible scripts (which is machine-readable documentation). Depending on your organization skills, even hand-written notes or making your own “meta” software packages (with only dependencies & install scripts) might work. What you don’t want to do is manually tweak a linux install, and then forget what is “special” about that server or what is relying on it.
• How safe is my setup? Depends… I still need to start rotating a mirror shard as an offsite backup, so not very robust against a site disaster; Security-wise… I’ve got a lot of private bits, and it works for my needs… as far as I know :)
• Still enthusiastic? I try to see everything as both temporary and a work-in-progress. This can be good in ways because nothing has to be perfect, but can be bad in ways that my setup at any given time is an ugly amalgamation of different experimental ideas that may or may not survive the next “iteration”. For example, I still have centos 7 & python 2 stuff that needs to be migrated or obsoleted.

Automate as much as possible. I rsync to both an online and home NAS for all of my hosted stuff, both at home and in the cloud. Updates for the OS and low level libraries are automated. The other updates are generally manual, that allows me to set aside time for fixing problems that updates might cause while still getting most of the critical security updates. And my update schedules are generally during the day, so that if something doesn’t restart properly, I can fix it.

Also, whenever possible I assume a fair amount of time for updates, far beyond what it should actually take. That way I won’t be rushed to fix the problem and end up having to revert to a backup and find time later to redo it. Then most of the time I have extra time for analyzing stats to see if I can improve performance or save money with optimizations.

I’ve never had a remote provider just suddenly vanish though I use fairly well known hosts. And as for local hardware, I just have to do without until I can buy a replacement. Or if it’s going to be some time, I do have old hardware that I could set up as a makeshift, temporary replacement like old desktop computers and some hardware that I use for experimenting like my Le Potato that isn’t powerful enough for much, but ok for the short term.

And finally I’ve been moving to more container-based setups that are easier to get up and running again. I’ve been experimenting with Nomad, Docker Swarm, K3s, etc., along with Traefik and some other reverse proxies so o can keep the workers air-gapped for security.

My incredible hatred and rage for not understanding things powers me on the cycle of trying and failing hundreds of times till I figure it out. Then I screw it all up somehow and the cycle begins again.