There are some private torrent trackers that have them. I got a 2020 site rip from Speed(dot)cd. TheGeeks is a tracker specializing in educational material, but I am not in it. Both are accessible through MAM but TheGeeks is a little harder to get in.
I could temporarily share what I have through a OneDrive link, it has 96 courses, ~400GB.
First I tried a few mobile apps, sticking with Sync for Lemmy for now.
I also went to Sub.rehab, filtered by highest active users and subscribed to the communities I was interested in. Then subscribed to a few I was interested in even if it has a low amount of users.
Awesome work! Anyway to include release notes with the update on the play store? I'm a sucker for those!