But how would one backup their self hosted apps? I imagine a cron job to create snapshots then upload them to a cloud provider. Isn't there a self hosted app for that as well?
Configuration I tend to store in a git repository that I back up.
For the VMs/whatever, I just document the setup and, in the case of a disaster, would just rebuild. It'd be a gigantic PITA, but the data and configuration are the important bits. The rest is just labour.
That said, this is why I don't self-host truly critical infrastructure like email or messaging. Everything I run are things I could live without for a while if I had to.