My first thought was the MIDI -> OUTPUT setting With the H9 as the slave, OUTPUT = THRU, and with the H9 as the master, OUTPUT = XMT. Matching the MIDI Channels is good practice for Programs Changes, CCs, PitchBend, … But MIDI Clock (when properly configured) transmits across all 16 MIDI Channels, by design.
Now, some synths send out MIDI Clock continuously, while others may need something ‘started’ (arpeggiator; step sequencer) to begin transmitting clock pulses. There’s a cool little feature-ette in the PitchFactor that didn’t make it to the H9: If you attempt to select MIDI -> CLK IN -> ON – and there’s no MIDI Clock signal detected – the PF display begins to flash. It’ll keep flashing until it’s sync’ed to a MIDI Clock. A troubleshooting technique that’s much faster than hooking up to a MIDI / Sysex monitor.
Unfortunately, Arturia isn’t very complete with MIDI documentation. I understand the analogue focus, and the manual is a great beginner primer on subtractive synthesis & patch building. The Connection Software manual has MIDI listings for global parameter tweaks, but not much else. The bad news is … the MiniBrute doesn’t send or receive much (MIDI). I don’t think the MiniBrute sends out MIDI Clock, but it will receive MIDI Clock (from the H9) on its MIDI Input:
https://www.arturia.com/faq/microbrute/microbrute-midi-parameters
It’s a ‘polyphonic controller’ with extensive onboard controls, and that’s where your hands will be. Logically, my thought was [MiniBrute master out to H9 slave]. But apparently, it will have to go [H9 master transmitting to MiniBrute slave]. There are a couple of tempo tricks on the MiniBrute that might be useful in that MIDI routing.
