I downloaded AnkiDroid from GitHub last year. It worked well till today. It seems it got the update (potentially from Play Store), and I’m now on 2.17. At the same time, I got the “inaccessible collection” error that prevents me from using the app.
Is it even possible that GitHub version got overwritten by Play Store? If I download again from GitHub, will the same thing happen?
Another user also seems to have a similar issue that he/she downloaded the app from GitHub, but app got updated by Play Store https://forums.ankiweb.net/t/inaccessible-collection/40707
If you’ve installed AnkiDroid from the Play Store previously, and you didn’t turn off auto-updating, it makes sense that it would update your app. You can turn off auto-updates to avoid that (as was suggested to the other user).
Or I think [not entirely sure this will work, but it seems likely] if you uninstall through the Play Store (at least), and possibly also remove the app from your “Library” – the Play Store should leave it alone, because it ignores side-loaded apps.
Make sure you have your collection synced/backed up somewhere safe before you start messing around with versions that are before/after storage migration.
It seems like you could spend a lot of time trying to prevent the update, but you’ll have to do storage migration eventually, so you might as well take care of it now and then you can stop fighting. Storage Migration FAQ · ankidroid/Anki-Android Wiki · GitHub