UEFI boot-repair not working

[ManfredB]

I have installed Debian 12 on a new SSD after my previous Debian 11 disappeared due to bit-rot of a SSD.
Also on the system, on a different drive is Windows 10.
The Debian 12 install did not detect Windows and I ended up using legacy boot.
Now I want the dual boot back again, preferably using UEFI.
I have a Debian 12 live USB stick with boot-repair installed on it.
boot-repair finds Debian and Windows and makes reasonable repair suggestions but then it fails with

Please enable a repository containing the [grub-efi] packages in the software sources do Debian GNU/Linux 12 (bookworm)(/dev/sdb2). Then try again.

The boot-repair log file is in: https://paste.debian.net/hidden/db8df863/

According to Google, several people have encountered this problem but none have received an answer that would allow boot-repair to succeed.
Any ideas?

[sunrat]

For Debian GRUB to detect other OSs you need to enable os_prober which is disabled by default. Boot Debian and change it in /etc/default/grub . You don't need boot-repair or a live disk to do this.
There are a number of topics about this already.

[ManfredB]

For Debian GRUB to detect other OSs you need to enable os_prober which is disabled by default. Boot Debian and change it in /etc/default/grub . You don't need boot-repair or a live disk to do this.
There are a number of topics about this already.

changed /etc/default/grub to:

GRUB_DISABLE_OS_PROBER=false

then ran

update-grub

not the slightest difference, windows not detected.
also tried

update-grub2

no difference either.

I also fail to see how this would allow me to get UEFI boot to work.