Can you tell me why the AP nodes need to be in stock firmware and not Merlin? For that matter, I remember people saying that a Mesh node needs to be in stock firmware as well, but I never understood/seen a "why" it needs to be in stock mode. Thanks.Do you still have AX88U main + 2x AC86U nodes?
If yes - there is nothing to update for you here. Keep the nodes on stock Asuswrt and update your main router to 388.2 when available.