Same problem with iMac - got 5k mostly working and a patch for audio using my favorite coding assistant, but that final bit remains tricky. Will post to GitHub if I can solve it.
ChatGPT just found a solution to the sleep problem - but it only works if I deactivate wake on wlan, which would defy the purpose of enabling suspend for me (I use it as my remote development box, want to be able to ssh into it and don’t have any cables in that room).