It doesn’t appear like I can edit the OP so I cannot remove outdated stuff but:
It’s done.
Thanks to two forum members who kindly donated Checksums, one of which had a different file that made me realize I had redundant and deprecated files (Thanks Gmod for keeping a version of the Summer Lobby for every rename in the Workshop! I was totally not unnecessarily confused!), I now have an archive of every .gma file that has ever been part of my GMT experience, maybe even every publicly released one.
Here’s the SHA1 as well as SHA256 hashes of them, password is again the SHA256 hash of “gmod_tower_ball_race_content_144365670.gma”:
The old policy of not sharing the files themselves stays the same since PixelTail haven’t changed theirs either (Duh!), same applies for posting the hashes publicly.