Thanks!

The adapter ends female to mate with the male built into 568, so I will purchase this DB9 and attach Cat8 wires as you’ve described.

Now I won’t need to tie up an excellent surround unit just for comms because of all of your (plural) help on this forum.

Server: Audiolinux Roon NUC w/HAF room correction and crosstalk cancellation
Theater: 218, Allo Signature, miniDSP, HD621, C61R, DSP5200SEu, 420, 33, NHT subs
EtherREGEN w/Finisar fiber, Shunyata Denali
Living Room: RPi4 Diretta Host & Target, Ghent USB > Singxer SU-6 > AES NA M-Links > DSP9
Shunyata TritonV3, LHY lps, Farad Super3, Stack AUVA feet