If you're just looking for personal sync (as opposed to collaboration), Syncthing [1] is a common recommendation, though personally I've had better luck with Unison [2].
However I should clarify: One of the reasons I want to move my data to a cloud server is that I am running out of space for more hard drives on my PC.
So syncthing will work for editing stuff on my local and syncing the changes with my cloud server. But I don't want to store all my data on cloud _and_ on my local PC. I want something where it is usually stored on the cloud server, but where I can bulk edit/organize the data selectively on my local machine.
Is Microsoft better than Google? Probably not. I don't know of any open source or self hosted solution this robust. You might want to consider getting a NAS; which lets you mount a network share on your local PC and use your normal file manager.
But I plan on also doing backups with blackblaze or somewhere similar.
My plan for the cloud server is just to have a central place to access all my (and my wife's) files from any device. But then my problem is, as I mentioned earlier, how do I bulk edit/organize those files using desktop software?
- Install git-annex on your cloud
- Tell git-annex that you have a remote there
- Do your stuff on your local drive, push to the cloud when it's done
- If some of the files are not needed locally, tell git-annex to drop them from your local drive. git-annex knows that there is another copy in a safe storage
- If you want to work on some files you don't have, ask git-annex to transfer them to you.
The manual steps might be a bit tedious, so git-annex also has an assistant mode that is a good-enough copy of dropbox (https://git-annex.branchable.com/assistant/). See the archival walkthrough, that seems to fit your use case (https://git-annex.branchable.com/assistant/)
(I have more or less the same need, but haven't committed to doing it just yet)