Hmm, I found an answer on Reddit saying "no, it's not possible without downloading" from 3 years ago with a justification that I guess I can appreciate but still disagree with "It forces you to listen front to back old the album like the old days":
https://old.reddit.com/r/BandCamp/comments/5snoms/shuffle_collectiondesktop_app/
I tend to listen to albums this way anyway, but in my special case, I have nearly 250 albums dumped in my account now (my fault, I acknowledge) and I just want a sampling from each of them without completely eliminating my computer's disk space... oh well. Maybe I'll just use a giant flash drive or something.
This is *exactly* the reason randombundlegame.com got built for the BLM Itchio bundle last year, though!!
lmao am I really gonna do this:
https://framagit.org/Ezwen/bandcamp-collection-downloader
(yes, probably)
Well that overloaded my flash drive, so I guess I gotta do it straight to hard drive and move it over instead...
Also note, if you use this downloader, you need the Java Developer's Kit (JDK) version instead of the regular Java Runtime Environment (JRE)!
Oh my god. I'm an idiot. The BandCamp app for iOS can shuffle your whole collection. It just wasn't clear to me because I'm not used to the heart icon representing my collection π
Oh dear this is going to take absolutely forever