According to Blu-ray.com, the new Criterion release will be in the 1.66 aspect ratio despite not being the negative or theatrical intended ratio.
Multiple Maniacs is also 1.66. It was shot full frame and cropped for theaters. 1.66 is an in-between point leaving more room without revealing the entire frame. It would have been exhibited in Europe that way as well. It’s not known if Pink Flamingos was shot “protected” or if any aspect ratio was in mind, but it’s clear it works 1.66 or 1.85.