I just purchased a new Lenovo 7 14 (flip). It came with Windows 11 (factory bitlocked).
The first thing I tried after going through the Windows 11 configuration/account registration is see how compatible with Mate it was.
Everything works perfectly. Track-pad, keyboard (special function keys), touch screen, wifi, bluetooth, audio, camera.
After the quick 10 min test I attempted to reboot into windows. I did not attempt to install Ubuntu MATE.
That was when I was greeted by a blue screen that indicated Windows had detected an alternate operating system had accessed the hardware and locked the drive and then forced me to enter the bitlocker recovery key to continue.
Fortunately I had a second device that I could do go to my MS account and do so.
My HP Probook did not do this, which is also running Win 11 but it is not bitlocked.
It was exactly this that drove me to Ubuntu-MATE. I made a lubuntu Live-USB for our old laptop that drives the TV (it was running Windows 7), tested it on my ASUS laptop - and couldn't get back to Windows 11.
Bit late to the discussion - this behaviour might be sort of expected by design.
The TPM chip in the computer stores a little secret to unlock the drive across power cycles. Booting a new, alternate OS not seen/trusted may "trip" TPM so Windows demands the BitLocker Recovery key to get back in.
That could be a good thing, in case someone was able to boot an alternate OS to tamper in a way that compromises the security of the original system. But I can see how it's annoying or gives the impression of Microsoft trying to lock down their hardware to Windows.
Apparently, this might be a security policy on the system: