Yes, secure boot is set to Other OS - if set otherwise there’s a message after grub that secure boot is active, so pretty sure about that.

Unfortunately it doesn‘t show anything, even with no parameters at all. The only thing that shows up when changing the grub parameters is the „booting a command line“ message which stays there forever, nothing happens.
I‘ll record it with my phone when I get home later on today with the nomodeset parameter.