dual boot – 22.04.1 forces EFI, making existing MBR system unbootable

I have several older dual-boot systems. The other OS is irrelevant to this question. I use MBR system drives, because EFI is a nuisance when I want to boot from CD or USB. On one machine, I had 20.04.05 and let updater upgrade it to 22.04. After a few updates, the updater’s package system became hopelessly broken, so I decided to reinstall 22.04.1 from a thumb drive.

I selected “something else”, and selected the existing Ubuntu partition as mount puint “/”. I ignored the EFI warnings because I do not want EFI. Install crashed trying to stuff EFI onto the drive. After that, the system drive was unbootable (Grub rescue mode*), and had to be reimaged from backup. Same result if I select automatic overlay of the existing Ubuntu partition

I ended up installing 20.04.5 for now. Drilling through the EFI warning wipes my Grub customization, but it does boot MBR, so I can fix Grub easily.

Is there a way to stifle forced EFI and respect my existing MBR/Grub setup when installing 22.04.1?

*The solution may lie here, but I have no idea how to proceed.