This looks like the initramfs is missing a driver for root drive controller. Do you have a backup, by chance? Replacing the initramfs /boot/initrd.img-6.1.90-1-amd64 with any previous version should work, so then we could check which module is missing.
Also, from this initramfs prompt you have on the screen, as suggested in one of the log lines, can you show the output of:
cat /proc/modules
This should list the kernel modules embedded in this initramfs. When you get the NUC up with either another initramfs or a new image (it can boot from USB stick?), we could compare this with the modules loaded on the life system:
lsmod
Theoretically a needed driver could have been removed from the new kernel build. Though this would be highly unexpected, or more a mistake then by intention. But can be checked, when we know which driver/module it is.
Thanks for the reply, but I am unable to perform any of your suggestions as I’ve already wiped the NUC and reinstalled. Time was of the essence, unfortunately.
Perhaps if others experience the same issue, they might find your suggestions helpful.
Good, if the new image works, then at least we know that the kernel is not missing any driver in particular. Probably there was some (hidden) error during initramfs generation, I/O issue with the drive or a bad intermediate kernel version. Just in case, keep a backup of the one that currently works, so you can theoretically restore that in case it happens again.