Here is a solution which solved the problem on my Samsung Full HD TV, when using it as a monitor for the laptop:
https://www.samsung.com/au/support/tv-audio-video/hdmi-pc-connection-text-is-fuzzy-image-isn-t-clear
Now I quote:
Why is the picture unclear or text fuzzy when connection PC to my Smart TV?
Last Update date : Oct 20. 2020
Common complaints when connecting a computer to the TV are either the text on the screen is fuzzy or that images seem grainy. This is because the TV's scaling is set for standard HDMI input. To resolve these image issues, you simply need to rename the input to PC or PC DVI. Once renamed, the TV will adjust the scaling of the input. Naming your TV's input can help you remember what is connected to each source.
Please note: Naming an input PC or DVI PC (or PC DVI) will change the scaling of the source and improve the picture quality.
Follow the instructions below to to name your TV source:
- Turn on your TV and press the Source button on your remote control.
- Use the navigation keys on your remote control select the source you would like to rename.
- Once selected press the Tools button.
- Scroll and select Edit name and then press Enter.
- Select the name for the input from the available list and press Enter.
Please note: You cannot enter any name but you may only choose from the available list.
- Exit the menu and your input will now be renamed.
Important: Use HDMI port with DVI port for PC connection, this is the input intended for PC connections.