Mint Mate 21.2, HDMI Scaling User Defined (1,4) sets back

[visionhelp]

(With Search I did not find this topic here in the forum.
For neighbour.)

Mint Mate 21.2, Display:
HDMI Skaling ´User Defined´ (1,4) is being back setted to the before pre-setting. After reboot.
(Maybe the word in english is: Fractional Scaling. (This Mint Mate is in german.))

What I fast could find (in internet) is: the xrand command can help this. But varies very depending on which hardware / software.

 

[dos2unix]

Which graphics card?

 

[visionhelp]

As to see in this contribution https://www.technipages.com/linux-mint-configure-output-resolution/ - I found now fast, for to show the screen-photo, what it is about - and some tips.
But to change things in the Boot Loader to me it goes a bit to far.
The command ´xrandr´ could do it already. But I cannot build this command by myself.

The pic from this site for to show, what I mean:

It is about the ´User interface scale.
I set to 1,4 for the TV shows exact the whole screen as on the laptop. (Else it is much to small.)
But reboot sets it back to as before.

 

[visionhelp]

Here it appears to be going into the right direction "Then run the following code in a Terminal window" from https://unix.stackexchange.com/questions/253449/multiple-monitors-hidpi-scaling

But with ´xrandr´ there are many things possible to set with.
But only need the scaling 1,4 to set there, I think. And the output data the device(s).
(It´s about a neighbour´s laptop, which can last some days, to get the xrandr infos for this. So no hurry.)

(If ´DP-1´ and ´eDP-1´ is always this same, no matter which TV: OK.)
Just to set the scaling to 1,4 all works well. Except, that after reboot this setting is setted back, does not stay.

Reading further in this link, this could it be:
"xrandr --output DP-1 --scale 1.5x1.5", but for me: 1,4.