i cant install the twrp because the phone says “only official released binaries are allowed to be flashed (recovery)” when i try to flash it, both heimdall and odin
here is what it says on top of download mode
RMM state: Prenormal
FAP lock off
OEM lock off
in settings, OEM bootloader is enabled, usb debug enabled
I too went through this. At the end of it we believe it had to do with a Knox feature that blocks flashing till it can be determined that the phone was being used in the Samsung intended geographical zone. I was using an Exynos S9+ in the USA and once the stock ROM was updated to Android 9 or above I couldn’t get RMM prenormal cleared, the result was forced blocking of any flash to the bootloader.
ok i managed to get rid of RMM using this method:
1. Turn off all auto updates in settings (automatic system updates in dev settings, autosync, and software update check) and Play market.
2. Change date to 1 month ago.
3. Reboot and turn on autosync in settings.
go into download mode and check if RMM is gone
try to repeat again if it didn’t work
method works on last security update
i’m using /e/ right now, good system, everything runs good 
Curious, what version of Android were you on when you did this, Oreo, Pie, or Q? What country are you in? Glad this worked out for you.