My email reply created a new message thread. The issue investigation with resolution is here: https://lists.iem.at/hyperkitty/list/pd-list@lists.iem.at/message/VQEGQBMGGW... Essentially an icon format issue.
One thing I still have to check, it looks like for the 8-ch ADAT Audio the adc~ inputs are reading in the dac~ outputs (instead of reading the incoming audio); so really ADAT output works now, input will need an extra look. When using analog stereo I/O, both input and output work ok.
Wolfgang