If you don’t want to go all out you can always just skip iCloud. You can quite easily synchronise your photos, Callander and so on with other platforms.

I’m currently on an office365 business plan though not for privacy reasons, but since it came with a terra byte of OneDrive storage I put my pictures there and not into iCloud as I didn’t see a reason to play two cloud platforms a monthly storage fee. Works just fine, and it also worked just fine when I was using g-suite and not office365 ans I imagine it’ll work just fine if you set up your own storage as well.