In my usecase i tested unraid, ubuntu server and xpenology fits Perfekt for me for example with the photos app. I have a real small NAS DS218j running 24/7. My xpenology server runs like 4 hours oder night or automaticly longer if needed. The smaller one syncs easy to the otter ones. Also create and recover Backups is easy there.

I use xpenology. You can save money if u use that.

This is also what i dont understand. I thought there should be a indexer but i never found one.

Are there Forums with the tenfingers URLs or how does this work?

I use yunohost for this. Ist possible there to use the sso etc. The default Installation Help to make a Quick and secure Installation.