Dream Theater and Classical music have entered the chat
Was actually confronted with the same problem - thank you for the solution!
I’ve been contributing to it via Street complete (can get it on fdroid) and it has become quite a hobby of mine.
It seems to be file based, so wouldn’t it be able to use other self-hosted sync-tools like the next cloud client (given you’re hosting your own instance)?
I understand a complete server reset would be inconvenient.
I’m quite fond of veracrypt: It offers good encryption and is transparent when mounted.
You can create and mount a container file with veracrypt, copy your existing data in there and replace the original folders with appropriate symlinks. I think thats the best tradeoff for good protection and convenience