Quote Originally Posted by dragonfly41 View Post
Other than that I would install rEFInd and in BIOS (F2 or F10 or whatever when starting up) select that as your primary boot option. It does not replace Grub. They sit side by side as boot options in BIOS. I always use rEFInd.
Yes, rEFInd is a good recommendation, especially that it can be used as bootable usb (without installing)
Also, rEFInd offers an option to boot the Ubuntu kernel directly, in effect, bypassing Grub.
Certainly worth trying.
https://www.rodsbooks.com/refind/
https://www.rodsbooks.com/refind/getting.html > A USB Flash Drive Image File