The atkmm 2.36 series is a new incompatible ABI series. It is
unnecessary for gtkmm 4 and is believed to not have any users.
Therefore, it's not worth packaging.

I am adjusting the debian/watch for atkmm1.6 to only watch for 2.28.x
releases which is the recommended stable branch for gtkmm 3.

Thank you,
Jeremy Bicha