Playback and USB MIDI keyboard won't work together

To get this out of the way, I have done everything suggested in https://musescore.org/en/node/96811.

System details:

Intel i9 11th gen processor and relevant hardware
Korg MicroKEY2 37-key USB MIDI keyboard, plugged directly into USB port on computer
OS: Ubuntu 22.04.1 LTS, Arch.: x86_64
MuseScore version (64-bit): 3.6.2.548021370, revision: 3224f34
Focusrite Scarlett 18i8 with PreSonus near-field speakers plugged into balanced 1/4" outputs on the Scarlett

Summary:

I have been using a MIDI keyboard to re-pitch notes. The original and expected behavior was that I could hear the notes as I was playing them, and Musescore played the score as expected. Today, this was no longer the case.

After running through the troubleshooting link above and trying a few things, here's what I found: when the I/O is set to ALSA, I can use (but not hear) the MIDI keyboard. The playback button works but there is no sound. If I switch I/O to Pulseaudio, I can hear playback but the keyboard stops working altogether, even after resetting the MIDI button, resetting audio, factory reset, et al.

Note that after every change, I've closed Musescore and re-opened it with my keyboard powered on to ensure it finds the keyboard. Sound is also working fine in other programs, and the keyboard is detected and working in Ardour.

The only thing I've done differently in the last 24 hours is that I have opened .mscz files that I downloaded from a sheet music search on this site, which I would hope to have no impact on my I/O (especially after a factory reset). Regardless, the issue and my workaround apply whether I'm in one of those scores, one of my own, or a new score.