If you're interested in switching over and that's the only hang up, I can give a few solutions a try on my machine at home this weekend and let you know if there are options for you that might not have come up through forum posts.
I know a lot of times when something gets added and "just works" no one bothers to talk about it so you don't know until you poke around yourself!
I ended up having a bit of time (and remembering ), I would second what u/ProletarianDictator said. Celeste (which can be found on FlatHub and is fully free) seems to do exactly what you're looking for, checking for updates to files in the cloud or on your machine constantly and pushing/pulling as needed.
I will say that the method is... rough right now. Assuming you're working with a modern system you should be fine, but if you're on laptop you might not want it running 24/7. Rather than waiting for changes to occur and then sending the data around, it seems like it's constantly checking to make sure the local/remote files are staying in sync.
It's all open source though and works very smoothly, so I'd definitely give it a try!
Edit: I also want to note that I specifically checked that the files are really located on my machine - I can confirm they are present in both locations and after severing the link between directories, the files persisted in a usable state on both ends. The drive integration as part of GNOME does not do this and I confirmed that.