Right now IEMs (in-ear monitors) are really popular at the budget level. They've come a long way in recent years and a lot of Chinese manufacturers are delivering them at a low price point.

There's no consensus of which the "best budget headphone" is. IMO it's the Koss KSC75 for $20, but that's just one opinion and you could argue that the sound quality is put on the backburner because the build quality is bad.

I have one pair for my desk which I use for "critical listening" and gaming. That's my Sennheiser HD8XX. For mobile use, I use airpod pros. The convenience is just so good. For my steam deck I use the Koss KSC75.