linux 6.1 video distorded

is it distorted in the text mode or in X-windows?

What kind of monitor are you using.  Some older, cheaper, or smaller monitors cannot display even some of these setup video modes.  I recommend you try another monitor to do your setup.  Then later you can work with X until you get it working woth the original monitor. If you are using a monitor that can't support 800X600 resolution or above, it won't work.  I had that problem with an older monitor and had to use another one to do the setup.