What is wrong with a Synology NAS or TrueNAS? Plenty of apps for photos on or using such.I am falling in love with NextCloud for many things reasonably integrated together. Can definitely self-host that and share it or parts of it with others and collaborate with them if you like.
Dockerize all the things. That and/or kubernetes. I hear nice things about Proxmox in home labs but haven’t got around to messing with it.
A lot of very useful software is not multithreaded. Hell, javascript is not multi-threaded.