- I have to go on a road trip to Warwick shortly, back around my midday or 12:30pm my time (1:30 your time)
In the meantime, you could do a couple of things with your /etc/default/grub , update it, reboot and report back on any outcomes.
(this is the standard, as @osprey
mentioned at #39)
2. With the line
try it with and without a # at the beginning, updating grub in between times. And a 3rd time (regrets) with no line at all.
With the line as you have it, it should be
generating a blurb saying from what it is instructed by /etc/grub.d/30_os-prober , which is
"os-prober will be executed to detect other bootable partitions. Its output will be used to detect bootable binaries on them and create new boot entries."
Have you seen that blurb before?
3. Your #46 I will deal with a bit more later, but if you type in the last entry with
apt policy grub-pc-bin
see if it has a line referencing
If you decide to take a look at that file, attach yourself to the end of a strong rope anchored to a solid object and wear a pith helmet, because it is a text file about 3MB in size and you might not come out alive otherwise.
4. If nothing productive, update-grub is a stub for a longer command
sudo grub-mkconfig -o /boot/grub/grub.cfg
mentioned earlier by @dankobatina
, and you could try that. There is a small chance the stub could be broken, but I would doubt that.
Back as soon as I can.