Sebrofnella

And I missed the obvious mapping of the MIDI CC to the dedicated tap tempo switch!

Sorry to contradict, but the H9 most definitely can respond to a MIDI CC to access the tap tempo function. In the H9 app, go to Pedal > MIDI Settings> Assign MIDI CC messages to pedal functions. Tap tempo is the fifth option down, you can choose the CC number and then assign a Helix Foot switch to a momentary transmitting the same CC on the correct MIDI channel.