u/IndependentBlood9969

I want to upscale an image so that it'll look better as a poster, and was just wondering if theres a specific upscaler I should use for digital art? One of the depicted characters has freckles and when I upscale the image they turn into random smudges on her face, and ive tried multiple models and websites and they all gave me the same result, so maybe im just picking the wrong models? If theres any upscaler yall recommend for anime/comics/line art please tell me :3

(edit: forgot to mention this but it has to be free to use and go to at least 4x)