grub entries for boot partition gone after bios change

I'm running KDE Neon 6.3 on a Ryzen 7 laptop, and yesterday after an accidental change in the BIOS (to CPU settings AFAICT) now on booting up the entries to boot are gone from the grub menu. I'm typing this from a live USB session, I was able to mount my partitions and see that there's no changes to etc/fstab or etc/default/grub. I've seen a lot of similar queries and posts related to other distros or dual boot setups with Windows but I'm not sure how to proceed and don't want to use the wrong advice. I have 2 physical SSDs, with the root partition on one and the home & swap partitions on the other, as below: Filesystem Size Used Avail Use% Mounted on tmpfs 6.1G 18M 6.1G 1% /run /dev/sda1 2.8G 2.8G 0 100% /cdrom /cow 31G 321M 31G 2% / /dev/disk/by-label/writable 4.5G 1.7M 4.2G 1% /var/log tmpfs 31G 0 31G 0% /dev/shm tmpfs 5.0M 4.0K 5.0M 1% /run/lock efivarfs 128K 43K 81K 35% /sys/firmware/efi/efivars tmpfs 31G 4.0K 31G 1% /tmp tmpfs 6.1G 1.6M 6.1G 1% /run/user/999 /dev/nvme1n1p2 1.8T 716G 1.1T 39% /media/neon/data /dev/nvme0n1p2 1.9T 68G 1.7T 4% /mnt/rootdisk This is my /etc/fstab: UUID=E08D-7C64 /boot/efi vfat defaults 0 2 UUID=67ab5efd-76af-465d-8aaa-e882e1207b01 / ext4 defaults 0 1 tmpfs /tmp tmpfs noatime,mode=1777 0 0 UUID=cd616b39-79ef-4e8e-827d-7507f6392d88 /home btrfs defaults 0 0 UUID=5ab1ff44-cb6b-472b-a724-9d1da73a0d1a none swap defaults 0 0 This is my /etc/default/grub: GRUB_DEFAULT=0 GRUB_TIMEOUT_STYLE=menu GRUB_TIMEOUT=10 GRUB_RECORDFAIL_TIMEOUT=$GRUB_TIMEOUT GRUB_DISTRIBUTOR='KDE neon 6.2' GRUB_CMDLINE_LINUX_DEFAULT="quiet splash resume=UUID=5ab1ff44-cb6b-472b-a724-9d1da73a0d1a" GRUB_CMDLINE_LINUX="" # Uncomment to enable BadRAM filtering, modify to suit your needs # This works with Linux (no patch required) and with any kernel that obtains # the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...) #GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef" # Uncomment to disable graphical terminal (grub-pc only) #GRUB_TERMINAL=console # The resolution used on graphical terminal # note that you can use only modes which your graphic card supports via VBE # you can see them in real GRUB with the command `vbeinfo' #GRUB_GFXMODE=640x480 # Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux #GRUB_DISABLE_LINUX_UUID=true # Uncomment to disable generation of recovery mode menu entries #GRUB_DISABLE_RECOVERY="true" # Uncomment to get a beep at grub start GRUB_INIT_TUNE="480 440 1" GRUB_THEME=/boot/grub/themes/fallout-grub-theme/theme.txt How do I restore the entries? As I could gather, there's something wrong with EFI. I've reset the BIOS to default settings and it didn't change anything. The contents of /boot are: -rw------- 1 root root 9080742 Feb 7 21:09 System.map-6.8.0-54-generic -rw-r--r-- 1 root root 287562 Feb 7 21:09 config-6.8.0-54-generic drwxr-xr-x 2 root root 4096 Sep 29 03:33 efi drwxr-xr-x 6 root root 4096 Feb 28 12:21 grub -rw-r--r-- 1 root root 142796 Apr 8 2024 memtest86+ia32.bin -rw-r--r-- 1 root root 143872 Apr 8 2024 memtest86+ia32.efi -rw-r--r-- 1 root root 147744 Apr 8 2024 memtest86+x64.bin -rw-r--r-- 1 root root 148992 Apr 8 2024 memtest86+x64.efi I'm guessing there should be entries for my boot partitions also here, since now my grub menu just shows me memory testing options. efibootmgr shows the following, with the live USB at the end: BootCurrent: 0008 Timeout: 2 seconds BootOrder: 0003,0002,0007,0008,0000 Boot0000* Windows Boot Manager Boot0002* ubuntu Boot0003* KDE neon 6.2 Boot0007* UEFI OS Boot0008* UEFI: SanDisk Cruzer Blade 1.27 I don't know why it says Windows boot manager when I've never had Windows on this laptop.