More efficient or even lossless, sustainable energy storage.

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!