I use the Sony a7rii on aperture priority because I use old lenses and there's no way the camera can stop them down (or open them up). I used the same system on my OM2 and OM4 again because it was the only auto mode. On my meterless cameras, I also use the same system of aperture priority, because I settle the aperture first and then adjust the shutter speed to suit.
The nearest I could come to auto ISO would be push and pull processing of the film - something I've never attempted in 60 years of using film. Except once with a new (to me) film which was an almost total disaster.