Can I be sure LL installer will not affect whatever boot process windows has?

[stevef]

Can I be sure LL installer will not affect whatever boot process windows has?

Even if someone reading this had exactly the same set up and had successfully done exactly what you propose it is not guaranteed that your outcome would be the same.  Dual boot actually requires some change to the machines boot process so to some extent you *need* to change the W11 boot process even if it is done in UEFI.

In your trial, the starting points have different hardware and OS.  If you'd had success it wouldn't really translate to success with a desktop W11 machine.  It appears something went wrong with the trial but, with the information provided, trying to guess what happened would only be speculation.