I just had a thought about the multiple profiles and syncing.
With NextCloud, WebDAV or Joplin Server (and I assume S3) it is trivial to create a new sync target for use by any additional profile by just creating a different folder to sync to as the folder is explicitly added to the target URL.
However on Dropbox (and I assume the same of OneDrive) the auth process simply creates a single "Joplin" folder in "Apps" which would make it impossible to use the same platform to sync multiple profiles.
Could there potentially be an enhancement here so that a second profile could have its own sub-directory on the target using the "Name" field of the profile?