Comment 8 for bug 1900917

Yep! Somehow, that little symlink appears to be the culprit.

I deleted my existing ISO, deleted the existing vmlinuz.efi symlink in my project files and then ran your snippet to comment out the vmlinuz.efi symlink creation in Cubic.

After having Cubic re-create a new ISO for that existing project, I put it on a USB and ran an install and the installed OS booted properly.

The grub.cfg file in this latest Linux Mint install show the proper "vmlinuz-5.4.0-52-generic" (NOT ENDING IN ".efi.signed") file and "initrd.img-5.4.0-52-generic" is properly listed on the initrd line right below that.

Thanks so much for your quick reply and quick thinking on a workaround. I know it'll take a bit more work to get Cubic working right for Pop_OS! and other Linux flavors though.