I’m happy to report that, as of today, krita-5.3.0-prealpha-1d2c802e14-x86_64.AppImage starts up as expected on all 28 of our Linux production systems. The bug report has been unceremoniously removed from bugs.kde.org, so I don’t know what was done to correct it, but YAY! It’ fixed!
Thanks, Krita dev team! Now, we can test 5.3.0 features effectively.