Current camera is an ancient Pentax K-7 with a dozen or so of vintage Pentax lenses – all manual focus because that's what I find fun. (Alternative explanation: I'm a hipster who's too poor for Leica.) I'd like to upgrade to a camera that isn't 12+ years old (i.e. doesn't become a white noise generator at ISO 800 and can capture 1080p60 video) while keeping compatibility with the lenses, ideally also the aperture mechanism and automatic aperture on the lenses that support it.

– Do I go Pentax K-3 III?
– I don't really fancy the size of an SLR. So are there any recent Pentax mirrorless options I've missed? Do other mirrorless cameras (Fuji?) work well with fully manual lenses?
– All my lenses are made for 35mm film. Any good full-frame mirrorless options you recommend?

Pic related: Pentax K-7 with a hazy-but-fun-as-hell Belarusian fisheye lens.