I've been stuck with RMM State Prenormal on my Galaxy A8 2018 for 3 months, waiting for this to be gone. Nothing to do, after 3 months of uptime, it still there.
Many tricks with time and date hasn't worked anymore, but finally I just success to bypass this s***.
What I've done :
_Install stock rom from original carrier (BOG for me, I were on XEF for deleting bloatwares).
_At boot, do NOT put your Google account and Samsung account, only Wi-Fi and that's all.
_When install wizard is finished, do NOT activate Developpers Options. Go directly at time and date, set it 8 days before after desactivate "Auto time and date".
_Go to System Update. Then untick "auto update" and check for update.
_Go back to actual time and date, check again for update.
_Only NOW, activate Developpers Options and OEM Unlock should be there.
It worked for me after MANY MANY tricks, attempts, and hopeless. This way given me another luck to root my phone and now I'm done and free with it.
Sorry if my english is sometimes bad. Hoping I've helped some users.
Edit : I did it on bootloader V3 (U3BRJ4).