Weird, the K4’s latest bios supports Vermeer, but perhaps not the X3D CPUs? But if so, even a 5600 would be an acceptable and pretty cheap upgrade over a 2600.

Which mobo do you have? Most of them got bios updates to support Ryzen 5000, even old B350s and some A320s.

Steam Deck is also only an 800p screen, so using DLSS/FSR will render the game even lower than that. Basically the upscaling just works better at higher resolutions since it has more data to use. And like you said, definitely better for farther viewing distances too.