This mod upscales in-game sprites using the xBRZ filter. It looks just as cursed as you imagine.
Should apply to most mods' textures as well. Affects only textures; has no effect on the text font, rounded corners on interface boxes and the game background.
Download: https://codeberg.org/TheMysticSword/Balatro-PixelArtUpscaler/releases/download/latest/PixelArtUpscaler.zip
Source code: https://codeberg.org/TheMysticSword/Balatro-PixelArtUpscaler