Judging the tone in here, this might seem controversial but we have supported a range of Windows-related as part of our scope. It usually comes down to one thing...
Basically if it falls under the scope of using Ubuntu with another operating system, it's probably okay here.
Examples of a valid interop question might be teaching Grub to allow to boot another operating system, or perhaps picking or using an Ubuntu native filesystem, or —he said crawling right to the lonely edge of the scope— consuming an Ubuntu service (eg configuring OpenLDAP to allow Win 10 pro logins). It's not off-topic just because somebody said Windows.
Your example question here is about straight up replacing Ubuntu. I don't think that has anything to do with us... But dual booting might be. I honestly don't know enough about how the bootloader on a Ubuntu touch device works.