Can confirm the clock assign outs on Mother will not run without the on-board sequencer running.
If you don’t have anything with midi-to-CV capabilities already (a Keystep? A MicroFreak?), it’s also possible, if sometimes fiddly (I recall there are ways that work better than others) to
Set the assign out on mother to a CC, like 2 (breath control), then use a DT MIDI track to sequence leading edges (exp envelopes I think?) as a clock, sending that assign out to DFAM clock. There’s an old post here or on Reddit where someone worked out the most sure fire way to do it, I’ll link it if I find it.
Here it is Tempo sync Digitakt, Mother-32 and DFAM - #10 by panpawel88 . I’d done it with a MIDI LFO and this way (a 2 step pattern with 127 and 0 cc values) is more reliable.