Moving dual boot Win10 & Debian 10 system from Legacy to UEFI

["Juan R. de Silva" <juan.r.d.silva@gmail.com>]

Hi folks,

I dual boot Debian 10 with Windows 10 from MBR in Legacy mode on my 6 
years old Dell M4800 workstation. The BIOS supports both Legacy and UEFI 
modes. With upcoming Windows 11 I am compelled to switch to UEFI mode.

I know how to switch stand alone Windows 10 or stand alone Linux from 
Legacy to UEFI mode. However I have not found how to do such conversion 
in case of existing dual boot install. I am not even sure if it is 
possible at all. 

I would endure Debian reinstall but unfortunately reinstall of Windows 10 
is not an option for me.

For now I'm planning to try the following:
- Wipe out Debian.
- Move Windows to free enough space and create a new GPT partition.
- Switch Windows to UEFI mode.
- Create new partition of suitable size and restore existing Debian image.
- Boot from any Linux Live-CD and install EFI GRUB module to restored 
Debian. (Another option would be installing EFI module in existing Debian 
system in advance and to make an image of it.) Reinstall GRUB.

Do you guys think it is actually feasible? Anybody can suggest something 
easier, smarter? It's a lot of work to do... :-(

Thanks.