Ah now I get you. It's one of the reasons why I also not bought into the nifty: It's modular is a great platform to switch out things if they don't work, but now it looks like you need to switch cases ;) .

My experience with midi clocks is, they tend to be a bit tedious in setting up. Reaper (DAW) for examples does not sent start stop or clock bei default, but it needs to be configured in the midi out.

From a quick search it looks like the clock needs to be activated seperatly from midi out on the elektrom rythm:
https://www.elektronauts.com/t/midi-clock-out-set-up/29559
But you probably already checked this