Another GRUB problem Debian

[Gallerilt]

I have tried all of the tips on grub, but without success. I managed to boot both debian and windows with rEFInd but after installing rEFInd to disk, it was not possible to at all boot windows.
So then it was just a matter of backing up the files on win10; reinstall windows, and suddenly it was fine to boot windows with rEFInd. Back to debian, start grub optimizer (!), and add windows, then everything works.
Lesson learned: don't be too quick to upgrade your OS; in this case to Ubuntu 22.04. DO NOT mess with grub! REFInd became a friend in need, but did not solve the problem.
The problem that remains: How to find the product key for my win10? The PC was bought with windows 8 pre-installed, can't track it down.

 

[Egzoset]

...after installing rEFInd to disk, it was not possible to at all boot windows.

Was the boot order modified? In any case i follow a simple rule: never allow any other system to touch Windows partitions, instead create one dedicated to 'rEFInd' as this is the "polite" thing to do dealing with Microsoft... Ideally also create an exFAT partition to share common data in transit between Windows and Linux.

How to find the product key for my win10?

It's been quite a long while ago but i gather you may be refering to « Bitlocker data protection » and more precisely the « Manage recovery keys » item accessible from your Microsoft account.

...