KDE Neon GRUB menu freezing after using boot-repair to fix try and fix GRUB Rescue prompt

Question

I'm not too familiar with Linux in general so please bare with me.

TLDR

I tried installing KDE Neon on an external USB hard drive, but when I tried booting my computer back into KDE Neon (not from the USB hard drive, the computer already had KDE Neon installed on its hard drive) I got the GRUB Rescue prompt. Attempting to fix this by booting back into the KDE Neon install USB and running boot-repair made it so now when the computer is booted, the GRUB "Select Operating System" menu appears but selecting any option caused the computer to freeze and become unresponsive.

I have a pretty old computer that I installed KDE Neon on a long time ago. I wanted to install a full copy of KDE Neon onto an external hard drive like what is done in this video. When rebooting my computer after this attempt and booting back into KDE Neon which was on the computers hard drive already, I saw the prompt for GRUB Rescue show on the screen which makes me think I mightove forgotten to change the boot loader installation device to the external hard drive, and may have left it on the internal hard drive that already had KDE Neon installed. To try and fix this I booted back into my KDE Neon install USB and installed boot-repair then ran the recommended repair all following this article. After this I restarted, and now when trying to boot back into KDE Neon which again was on the computers hard drive already, it showed the GRUB "Select Operating System" menu, but whenever I choose any option from the list, pressed C to open the GRUB console, or pressed E to edit, everything would just freeze and become unresponsive forcing me to manually turn off the computer using the power button. Is there any way I could boot back into my existing KDE Neon install on the computers hard drive again like I was able to before I tried installing KDE Neon on the external drive (which also didn't boot by the way)? Again the computer I'm using for this is very old if that matters. Thanks.

System Information
GRUB Version	Running grub-install -V on the KDE Neon install USB returns grub-install (GRUB) 2.06-2ubuntu7.1
KDE Neon Version	5.27
Ubuntu Version	22.04
Computer	Dell XPS 400 (Released 2005)
CPU	Intel Pentium D CPU 2.80GHZ

Answer 1

Turns out this is an issue with the breeze theming of grub which I was able to fix using this temporary solution.

The solution says to boot from a KDE Neon live USB, find the drive where KDE Neon is installed using fdisk -l, then run

sudo su
mount /dev/sda1 /mnt
mount --bind /dev /mnt/dev
mount --bind /dev/pts /mnt/dev/pts
mount --bind /sys /mnt/sys
mount --bind /proc /mnt/proc
chroot /mnt

and edit the file /etc/default/grub.d/99_breeze-grub.cfg by adding a # in front of the line that says GRUB_THEME=. Then run update-grub and the issue should be fixed until the next update.