Media Server? No content backup at all.
If you lose everything, just download new stuff you want to watch, or redownload a few TV series/movies.
Music? There are streaming services.
Only backup configurations and maybe application data, so that the reinstall will be easy. Those few kB/MB could sit anywhere. I’m using GitLab for this purpose.
Edit: Images! If you have your photos on there, back them up! They can’t be replaced!
A self-hostes RSS reader? Probably the ability to read your stuff from anywhere without installing something. Like on your work PC… ;)