I was doing just this for a while but stopped because my Mac Mini was too old for the last few OS releases. I then switched to using the Windows iCloud client but a bug from ~2 years ago that consumes tremendous CPU cycles made that less than ideal. (The best you can do is lock it to a single thread, which will then use 100% 24/7)

Now I just don't backup my iCloud, though I do remove everything older than one year every new years to my home server which follows a good 3-2-1 backup strategy.

TL;DR: If you go this route, try to get a Mac Mini that can run a supported macOS for some time to come.