Android 11 updates: Do I need to unlock the bootloader?

Hi all,
As my fingerprint on FP3 in combination with A13 is not working anymore and I desperately need to use ID Austria for some legal issues I finally decided that it is time to revert to A11.

Problem:
the link posted at FAIRPHONE 3 and 3+ A13 - Fingerprint sensor update is not working anymore. The article https://support.fairphone.com/hc/en-us/articles/360048050332 is not available anymore.
Can someone please send me a working link to the revert instructions.

Best Regards
Johannes