Hello Johannes, when using algorithms like the EQ Compressor you may tap the tempo using an auxiliary switch. As long as Tap Tempo is mapped to that switch in the pedal’s Aux Switch Mappings, the H9 will send MIDI CLK information to your downstream pedals.
Be aware that if you change into the “EQ Compressor” algorithm and the H9 sends out a program change to downstream pedals, those pedals will default to the tempo settings programmed into their algorithms because the eq Comp algo doesn’t send out a BPM. So, my advice is to program presets on the other pedals for when you’re using the EQ Comp, so they switch to the BPM you want. But otherwise, you will be able to control them from the H9 via a tap tempo switch.