Easy - disable Secure Boot
Windows 11 has Secure Boot as one of its requirements. Windows 10 does not care.
If you disable Secure Boot in the BIOS then at least the first few rounds of Windows Update should not try to downgrade your system to Windows 11.
(M$ may find too many people use this escape route and remove the Secure Boot requirement sometime in the future.)
Icon for what should happen to the M$ staff who keep tinkering with the UI rather than trying to fix the myriad of bugs in every windows release. ========>