I’m looking for a way of setting the timing of various delay plugins, using a ‘tap tempo’ feature. This is mainly for live performances, where I won’t know before exactly what tempo our drummer decides to go with. Ardour can present a generic UI for configuring plugings ( at least LV2 - I haven’t really tried any others ). I think Ardour should have a ‘tap tempo’ feature next to the ‘Delay’ settings ( though I guess they might be named differently across plugins ). Using a mouse to drag the delay setting around until it sounds correct is really not the way to do this live.
You should be getting any custom UI with LV2 plugins, unless there is not one and in that case there will be displayed a generic UI yes.
Ardour can’t tell if having a ‘Tap’ button is appropriate or not for a delay, and not all plugins have or name the same a ‘time’ port to give the time to. It is the job of the plugin to provide that functionality, not really Ardour. Ardour 3, iirc, will provide the plugin with the tempo and meter as defined in the session, and there are several ways to set that, including from a region length based off measure or beat.