The Nuphy has low-profile key switches with low key travel, and the height of the keycaps is at least as high as the key travel + thickness of the plastic + curvature around the lowest point.
If it is the flat profile you're after. you could get a Topre keyboard with MX stems: A Realforce RGB or Novatouch, or one modded with after-market MX stems. Then populate it with same-height spherical keycaps such as DSA, XDA or MDA profile.