Thanks @51lieal !
After swapping disks, this unicode.pf2 file hs been deleted automatically - I have never customized GRUB config. Fresh Qubes 4.1 installation had started without any errors.
This might be some sort of GRUB auto clean issue.
Just glad, aforementioned command will fix the Qubes boot entry. In the past I had … bad experience … fixing GRUB issues by hand:
