What's a good 4K budget graphics card?

I'm looking for a 4K Graphics card, but I'm wanting something that can handle 28-45 FPS on current gen and previous gen games at low to medium settings. I currently own an RX 570, which I think may work with most titles, but I'm not entirely sure. I'm also not too interested in future releases due to the rampant Micro-transactions, but if I do buy a new AAA game in the future, I'll be more than happy to downscale it back to 1080P if need be.

Sure throw 4K at your 570 using the games you want to play and see how it fairs :). If you are happy with it then no point in upgrading. It was never really designed for 4K though so don't expect much.

I had an RX 580 4GB and it got around 22FPS at 4K in rise of the tomb raider at pretty close to its highest settings (i think i couldn't max textures due to the lack of Vram). Not really playable.

I currently have a Vega 64 and it runs Shadow of the tomb raider at it's highest settings at around 35FPS at 4K.

I have also seen a GTX 1080 put in a solid showing at 4K in games like Doom 2016.

So if you are happy with the lower framerate something around the Vega64/GTX1080 level of performance will probably do the job for ya (not those specific cards mind unless you can find a really good deal).

A 5700 or a 2060 super could be worth a look at.