IMO you don't need to include the part about creating user 569. 568 still works without any acl modification. The real trick seems to be using the default storage settings while running the plex install from the truenas side. ixvolume for data and config, temp for transcode and logs. Then add the additional media libraries manually that the hexos plex installation created.
Caveat here is that this worked for me with an intel igpu (13400). I can't verify if these same settings fix the arc issues but they seem to from others comments. Trying to hardware transcode in the plex app hexos installed was a no go for all the same reasons listed above. Stopping/deleting that plex app and reinstalling another instance through truenas with the defaults i mentioned worked like a charm.
Hope it helps and that the hexos team can resolve this issue in the future 🙂
