I want to log in with Ubuntu on Xorg. Please How to do it?
Assuming Ubuntu 26.04, that’s not possible as was covered in the release notes for that release: Ubuntu 26.04 LTS summary - Ubuntu release notes. GNOME 50 no longer supports Xorg (same as KDE Plasma 6.8 won’t support Xorg).
For such questions it’s best to ask in the Ubuntu support channels first.