Share permissions on the upload folder are rwxr-xr-x. It has my username for both the owner and group. I don’t see how folder permissions could limit the type of file uploaded, though. The problem existed before I even installed the File Access app, and I installed it to try to correct the problem but disabled it when it became apparent it wouldn’t help.
I found a post with a similar issue here: Unable to upload certain file types... Ideas?. The poster’s solution was just to wipe and reinstall NextCloud, which I’m hoping to avoid if possible.
One thought: I am using sqlite. Could that be causing issues?