I installed a system update today, which included updating something related to the bios. I have a machine with linux and windows and I used grub to choose the OS to boot into. After the update, the grub screen doesn't show anymore and everything I get is a screen asking me to perform MOK management and the options to continue boot, enroll key from disk or enroll hash from disk. If I continue boot, I end up in Windows.
When I press F12 during startup and go into the boot menu, I can choose only from Windows Boot Manager and the Linux-Firmware-Updater \fwupx64 (which brings me back to the MOK screen). What do I have to do in order to get the normal booting routine using grub back so that I can use my Ubuntu again?