I set this up over a year ago on my Sony TV and it was quite the learning curve.
Firstly you must use an HDMI cable of at least 4K capability (preferably 8K just to be sure it's of sufficient display quality).
The other issue is, displaying 4K @ 120hz from your computer in Linux often requires enabling special settings in your TV. Often this does not come pre-configured from the factory to allow a 4K display @ 120hz on computers by default with Linux.
It took me a ton of searching to figure out which settings needed to be changed on my Sony 4K TV to enable 4K display over HDMI from my computer. I have no idea which settings a Samsung would require as most manufacturers use different terms and they are far from intuitive. There's no point in asking me about what your TV might require, as I do not remember the settings and I'm not currently using that TV.
The other issue I experienced (once I had the cabling and TV configured correctly) was that I could enable 1440p at 120hz, but it would not stick. Once I rebooted I had to reset the display back to 120hz from 60 every time after a reboot. No matter what I tried I could not get 120hz to stick. The only way I could get the 120hz display setting to permanently stick was to reinstall Garuda with everything set up 100% correctly during the install process.
It was a long and painful process to get things working properly as Linux doesn't seem to have implemented full support for this as yet. I also gather TV manufacturers don't seem to want this enabled at purchase as it may lessen the life of the screen.
Good luck to you.