I recently got a new s21 and wanted to install the one UI 6.1 software update. After the update I couldn't use the screen but everything was working. Turns out Samsung issued a new patch which blocks any second market screens from functioning after the new update. This is to ensure that all Samsung users go to authorised Samsung technicians for device repairs. The only fix was to reinstall the previous version (one UI 6.0) from my laptop and debug it by installing it using a data cable. Hope this helps anyone that doesn't buy their phones from Samsung stores.
Samsung and Apple have been doing this for quite some time. That's why you always ask the 3rd party vendors or shops if the phone has been fixed and which parts have been replaced and if so which parts they used OEM or Generic replacement parts.
