Right now Joplin supports syncing with OneDrive, Dropbox etc. I would like to recommend support for a service called pCloud which works in a similar way to all the others. But it allows for a one time fee instead of subscription payments which is attracting attention. It’s got an API already working so I wouldn’t suppose it would be very hard adding support. But it’s worth bringing up.
This topic is a duplicate of Feature Request: pCloud Synchronisation.
Closing this one. Head over there for all further discussions.