I found that the community-object drj/seq/seq_clk_sync does what I want.
It has a miditransport tickbox and lets you choose internal/external source and device, has a clock divider, all the bells and whistles.
However, I needed to create a separate midi/in/clock object in order to connect the "active" outlet into the "run" inlet to make it obey.
Oh boy, this is going to be awesome, I am already lovin' the Axoloti! Thank you Johannes for making this!