As gitlab kindly points out, this is my first time in NetworkManager, so take the following with a pinch of salt.
Perhaps it's not the most correct thing to do, yet empirically this patch is enough to get things working on my end. Assuming this gets merged, please consider picking it for all applicable stable branches.
Removing these restrictions gets 8021X networks (WPA-Enterprise + PEAP/MsCHAPv2) working on the Steam Deck.
So the inline comments are not 100% correct and the restrictions seem dubious. Drop them.