First run after anki update should trigger add-on update check

I’d recommend you just set a global variable to True whenever an add-on is toggled on or off. If it’s true, the debug info could show a line like “Add-ons have been enabled or disabled since the last time Anki was restarted, and the list may not reflect the currently running add-ons”. You could also make the message at the top of the add-ons screen turn red to make it more obvious.