Although syncthing is awesome, i use rclone to fetch the latest version of the password database. With syncthing, i would worry about collisions. Maybe would be better to sync it between two devices, Android and Linux.

Yes and no. You can store them in a free cloud account, provided you have local copies; there’s a risk your access to the cloud storage could be denied. A security risk is that they could harvest these databases, and decrypt them later.

I think your best bet, if you were to use free services, is to delete old databases from the cloud. Encrypt the new databases with the updated password manager and a new master password.