Coming rapidly after our last release, Ardour 2.8.14 includes just a couple of fixes:
packaging changes that make various plugin GUIs work correctly (notably the DISTRHO LV2 ports of TAL plugins)
Generic MIDI bindings to non-toggle controls using note on/off messages now work in a sane way. Previously, Ardour did something quite odd in this scenario. This enables several generic MIDI controllers to be used much more easily to control the transport state, and several other things too.
Bindings to the transport control buttons for return-to-start, goto-end and play-selection now work correctly.
What version of a given LV2 plugin set are you using? My guess is that you are using an older version that use a now-deprecated LV2 GUI extension, and that the newest release of CALF will work just fine. LV2 standards have changed quite a lot since 2.8.12 …