Version 3: TempoChanges and some built-in plugins won't show up on Plugins menu
Windows version 22.214.171.12415:
In the Plugins Manager, I checked abc_import, colornotes, createscore, notenames, run, scorelist, walk, and an add-on plugin called "TempoChanges" (whose containing file tempochanges.qml I put the file in the Plugins folder), The only plugins that then show up in the Plugins menu are "ABC Import" (for abc_import); "Notes" (for colornotes); createscore, and walk. Plugins notenames, run, scorelist, and the add-on TempoChanges don't appear.
Is this a bug? I've never actually used notenames, run, or scorelist, but I have used TempoChanges regularly in the past (with version 2).