https://news.mapcamera.com/KASYAPA/pentax_21_limited/
(in Japanese)
The test pictures were taken with a full-frame K-1 II, all posted sample photos are downsized to 10.7 mega-pixels. IMO, the image centre resolution looks good even when the lens is wide or near opened and that corner-to-corner sharpness is achievable when it is stopped down. However, I am not impressed with the dynamic range of the samples (which looks really bad) and neither the colour rendition of those. Let's see more samples to verify and judge in due course.