If you decide to not got the YunoHost route, I like the way this guide did reverse proxies with Caddy: https://github.com/DoTheEvo/selfhosted-apps-docker.

Definitely check this summary out: https://meichthys.github.io/foss_photo_libraries/. Everyone’s use case and priorities will be a little different, but I’d vote for Immich as a Google Photos replacement that looks nice and is very easy to use. I was awestruck by the facial and object recognition, which wasn’t even a feature I particularly cared about.

I have this scanner and agree it works great, although there may be cheaper options out there that also work well.

FTP worked well out of the box. For SFTP on Arch Linux, I had to follow the troubleshooting instructions here: https://wiki.archlinux.org/title/Very_Secure_FTP_Daemon#LIST_command_resets_connection.