Well if you're running 11 and it tells you 11 is not supported then....How did you do it man?
I got this error when I tried with your steps.
Device model is SM-N986B
CSC version : N986BOXM1CTL5
Android version : 11
Build date : Tue Dec 22 19:01:00 KST 2020
Country : MALAYSIA
Sales code : XME
Do I have to downgrade?
I am in SouthEast Europe,what CSC do you suggest to use?
Just use the Google dialer trick, install Google dialer, set as default and enter this code
Change to whatever CSC you want, backup first as it will wipe the phone