Yup sysdefault, and I had tried both default and force HDMI for Audio Output.
If you’re out of ideas, I’m triply so. This last worked on 2.51. I can try a fresh install on 2.53. Fresh install on 2.51 might be instructive as well, but I did not save that image. A quick jaunt through the max2play site didn’t find it. Are you aware of a download location for m2p_buster_rpi-v251 ?