I have dual boot on my Lenovo Thinkpad T420s, Windows 10 and Ubuntu 22. Actually I had, because I tried to reinstall Ubuntu 22 and I’ve lost my dual boot and ability to boot at all. So I tried few things:

• reformat manually EFI and root partitions
• os-prober and update-grub
• setting root and prefix at grub rescue
• grub-install
• Windows installation troubleshooting

Unfortunately it does not work. Something went terribly wrong. To bring back Windows first boot from installation media and go for command prompt:

diskpart
list disk
sel disk X # select disk with Windows installed
list partition
sel partition Y # select boot partition
detail partition # in case Active is set to No then...
active
exit

This way I was able to boot into Windows once again, but unable to do it from grub and unable to boot Ubuntu any more. I also tried the following:

bootrec /fixmbr
bootrec /fixboot # does not work
bootrec /rebuildbcd

So I decided to reinstall Windows as I keep only Office, Typora and Fruity Loops there so will be easy to bring it back. After Windows reinstallation I tried to install Ubuntu one more time, but… there is no option for dual boot installation! Why? I do not know for now.