Hi, Ramesh. This is just to close the thread: I figured it out! I had an additional application -- that doesn't show up under the Startup section of Task Manager nor as a Service under System Configuration -- that alters the default Windows 11 UI, StartAllBack. Disabling it solved the issue.
(In defense of my stupidity, I did consider it as a possible culprit when I first encountered this problem and remmeber disabling it at that the time to no avail -- I must have misclicked something. I should have uninstalled it from the get go.)
Thank you so much for all your help! Hopefully anyone encountering this issue can profit from your troubleshooting. Appreciate it!