@Dyceman, to access Recovery mode please follow the path below:
1. Turn off your device
2. Connect your device to the PC via USB (not to the charger)
3. Wait until the message that the device is being charged appears
4. Press and hold down the volume up and then power buttons and hold them untlil the device turns on
5. Recovery menu should appear
6. from there select "Wipe cache partition" (you can navigate using volume up/down buttons and confirm with a power button).
Well, i've received the Android 11 OneUI 3.0 update yesterday on my S20+ phone and I can't access it either! And I didn't get a beta, I got the real update.