Unfortunately you appear to be using two features that will cause this:
Fullscreen windows on the modeset Xorg driver: bug 1754284
Fractional scaling on the modeset Xorg driver: bug 1846398
The only ways to avoid the bars (screen tearing) on a system like yours would be:
* Choose 'Ubuntu on Wayland' from the login screen to avoid Xorg; or
* Avoid fullscreen windows and avoid fractional scaling, when using Xorg.
Unfortunately you appear to be using two features that will cause this:
Fullscreen windows on the modeset Xorg driver: bug 1754284
Fractional scaling on the modeset Xorg driver: bug 1846398
The only ways to avoid the bars (screen tearing) on a system like yours would be:
* Choose 'Ubuntu on Wayland' from the login screen to avoid Xorg; or
* Avoid fullscreen windows and avoid fractional scaling, when using Xorg.