Alright, I’ve given Photok a test. It seemed decent, but the two problems I found were that videos were very slow to load when viewing, and there isn’t any way to organize files or create folders within.
I did some more looking, and I found DroidFS (fdroid link) which seems to solve both those issues for me. It seems well maintained, so I think this is what I will use for now unless I find a better alternative.
Thanks to everyone that gave suggestions!