Ah - I didn’t realise it was a plot to airbrush VST2 from history I just thought it was a bug. (I guess that means VST2 has been ‘cancelled’ - to use the language of our time…).
Joking aside - to expand on the issue a little - the problem with this as I see it, is that you’ve done something which fundamentally changes the configuration - from a user perspective - e.g. something they added / installed (and possibly paid for) now appears to have been removed without them doing anything. Worse, from the point of view of third-party developers like myself, e.g. if a user installs a VST3 of one of my plug-ins, and their VST2 is then no longer available, it appears to them that I did something, or that by installing my software something has happened as a consequence, and I get unpleasant emails (it happens… and I’d prefer not to waste my time dealing with it) about what my software has allegedly done. I just thought it would be insightful to point out that some of these benign changes from a developer perspective have potential unintended consequences outside, or to others within the Ardour ecosystem. Other DAWs have similar ‘hide equivalent VST2’ options but its usually an obvious filter you can choose to switch on in the plugin selector.
Perhaps some kind of user notification is necessary - its clearly mentioned in this thread in the release headline, but someone installing / updating to Ardour 6 from a distribution will almost certainly not be aware of it
[EDIT] Actually the obvious (and more elegant solution) would be to add the checkbox to the plug-in manager instead (or you could just add the ‘hide equivalent VST2…’ option to the list of filters already available. That way, the option is presented to the user in exactly the place where its effect will be noticed. It could even be enabled by default in this instance. As it is at the moment, you simply wouldn’t know to even look for it if you didn’t already know such a thing existed (I was caught by it, with one of my own plugins…)