Game servers like Luanti or Veloren. For the personal Youtube, Steve on “Ask Noah” podcast has it set to automatically download new videos from a particular channel and he hosts that for his kids. My kiddos are older so I just host general services for them.

For work, we use Bookstack, you can use the api to export pages as markdown as a quasi-backup. At home, I have been using Jotty. It saves as markdown, organizes with folders, and has a decent mobile interface for when you’re on the go. I just use syncthing to sync the data directory (markdown files in folders) to my backup storage