How to adjust monitor refresh rate?

Question

Video cards

Hello.
There is a monitor LG 24MP59G-P Refresh rate 75Hz
Video card Gigabyte AMD Radeon RX 550 2Gb
System Ubuntu 18.04
When working on a computer, with any key or mouse press, the monitor flickers. (When moving the mouse, there is no such problem).
To get rid of this, you have to go to the Ubuntu screen settings, make the frequency 60Hz, apply and set back to 75Hz. Then the problem goes away.
What could be the problem? And how to get rid of it?

Answer 1

there were artifacts on ubuntu 20.04 - some monitors have a small range of scan and frame rates. I cured it by setting the necessary parameters for my monitor according to the guide.
here is the material for study:
- YouTube video
- HOW TO CHANGE THE SCREEN RESOLUTION THROUGH THE TERMINAL (los ...
For myself, I made these parameters. 60Hz is required, and a screen resolution of 1680x1050
is created a file that is set to autorun at system startup

#!/bin/bash
xrandr --newmode "1680x1050_60.00"  146.25  1680 1784 1960 2240  1050 1053 1059 1089 -hsync +vsync
xrandr --addmode VGA-1 1680x1050_60.00
xrandr --output VGA-1 --mode 1680x1050_60.00