MIDI transport/machine control over USB not working (Linux)

[Lava]

I cannot get my Roland JD-Xi or Korg Minilogue XD to start playing their sequencers in sync with Waveform 11 on Ubuntu Linux. It seems that MIDI transport/machine control over USB is not working. Hopefully I'm just doing something wrong.

I have the synths set as follows:
JD-Xi: MIDI = USB, slave, channel 1, Driver = generic
Minilogue XD: MIDI = USB + Midi, Clock Source = Auto, Respond to transport = yes

On Waveform I have the synths' MIDI inputs and outputs enabled and set to default. Under "Sync" I have it set to send MMC to whichever synth I'm using.

I can successfully record midi notes into Waveform using both synths. I can then play back those midi notes from Waveform to the synths and they respond. The Minilogue tells me on its screen that it's seeing clock from Waveform. So why won't the sequencers on the synths start playing? Is this feature broken?