If you tell me which your Fairphone 4 is currently running, I can give you the specific APK files or command lines for that update.
Because the Fairphone 4 has an unlockable bootloader (unlike most US-brand phones), you have more power than the average user. This method uses ADB (Android Debug Bridge) to delete the FRP database. Bypass Google Verification on FAIRPHONE 4
On most phones, a technician would charge you $50-$100 to flash a modified firmware to bypass FRP. On the Fairphone 4, because Fairphone provides official bootloader unlock codes and full kernel source code, you can actually flash a "pre-rooted" engineering boot image that disables FRP permanently. If you tell me which your Fairphone 4