KeplersConundrum, you're right: of course switching MIDI In Ports to Off blocks everything - including MIDI keyboards!
Sorry about my stupid mistake - working long into the nights on a major design update of my monster subsystem in Logic's Environment is not conducive to clear thinking during the day! I'd forgotten I typically don't use my keyboards at all when working with symphonic scores and so usually have all MIDI In Ports off to catch any accidentally unmanaged loops in my Environment design (which actually relies on carefully managed IAC Bus loops using non-standard routing).
Anyway, it's interesting that you've not eliminated stuck notes by switching off all MIDI In ports. And I agree with your pragmatic decision to shelve VEP, at least until we know the stuck note problem with Logic & VEP AU3 in Apple Silicon is history.
BTW I'm working with latest VEP AU3 with latest Logic in latest Ventura on an Intel iMac and haven't yet encountered stuck notes (although of course that's of no direct relevance to the issue in your Apple Silicon machine).