Have you heard of [syncthing](https://syncthing.net/) ? It syncs a folder between devices, like Dropbox, without the need for someone else's computer. No cloud, it's just your pc talking to your phone, directly and automatically, through your home WiFi.
I’m working on something that allows for custom CRDTs since I agree no one CRDT strategy is best for any given app. There are several others I know of but they only use a single type. I think Automerge is the most popular current one but I don’t know if it has many actual users.
Mine is Eidetica, still very much experimental but I’m making progress https://github.com/arcuru/eidetica