Updated my earlier post here
. The G.Skill 4800MHz was just delivered. Posted on XMP without a hitch.
G.Skill Trident Z Royal Elite 4800MHz 2x16GBP/N:
Tested with 2 sticks on Z590 Dark. Loaded XMP defaults and Gear 2, saved and rebooted, posted no problem at all.
Thanks rblaes_99 for the help.