TV displays can receive any PC resolution you throw at it, because they usualy have preconfigured multiple signal modes, every other resolutions you send are done by upscaling/downscaling to selected signal mode
as you can see here, connection to display is 4K, while desktop resolution is lower
that case where it refused to show image at 1440p could be because display drivers were sending incorrect active signal mode to that display, this can be corrected with cutom resolution
here some random google picture example how it should looks like in nvidia control panel
you can see 4k x 2k mode with six resolutions available, any 4K TV can handle lower resolution, including 1440p (under 4k mode)
mine samsung for example can do it aswell, but if i reconfigure TV factory settings a little, it is able to shows 1440p as signal mode aswell.. but then once selecting it up, it refuses to show picture, so i guess TV firmware was in that ONN case set incorrectly, which can be fixed with cutom resolution profile