To clarify, did they actually fail or did you just get a warning message? It’s possible that the install actually completed, but you got an error about the bootloader install (which isn’t meaningful). (or maybe it just requires an EFI system partition mounted somewhere…not necessarily the “right place”)
Also worth noting that once an install fails you need to reboot the install iso to reset things if you plan to try again.
If you’re getting the splash screen, and then a black screen beyond that…it SOUNDS like it’s booting, but there’s something off about the system. Can you use alt-1/2/etc. to get to a non-graphical terminal? Or boot into the installer and chroot, then do another update? I’ve seen a few other people with black-screen boot issues recently and it might just be a badly-timed update. Maybe disable Plymouth?