I'm skipping the 2.5.12 release of the snap (it's currently on 2.5.10), so it's certainly not that. If it was though, the answer to stop auto updates would be to download the snap directly (snap download joplin-desktop) and install it with the --dangerous flag, (sudo snap install joplin-desktop_local_file.snap --dangerous), avoiding importing the .ack file that has signature verification that ties it to the Snap Store. Such a snap wouldn't ever automatically update and they'd need to keep downloading and installing like this on their own terms.
I don't think Flatpaks automatically update at all by default.
I'm also very much under the impression that the AppImage just lacks the capability to do automatic update checking at all. There's no UI for turning it off because there's no functionality to do it to begin with, see #4102 and #4096 in v1.4.12
2 Likes