LostPistachio aka rianadon shared the case of his Limbo, an ergo split keyboard with keywell, modeled in Cosmos. Low-profile switches, vertical thumb cluster. Being a handwired board without a build guide or much documentation, you have to figure out the internals for yourself.
I think their ought to be more low profile, good-looking contoured keyboards. I love my big clunky keyboards but I'm not stuffing them in my backpack. So here's my entry: The Limbo. It has the same curvature as most dactyl designs but more aggressive stagger, since it's designed for the home row keys to rest right under my fingers when relaxed – LostPistachio.
Specs
40 keys (6x3+2)
Choc, hotswap
keywell
vertical thumb keys
As the author suggests, you can scan your hand and refit the keyboard in Cosmos – a tool developed by himself by the way –, "change the switches, add whatever gobbledygook you wish, or whatever". Here's a link to the configuration.
Limbo thumb cluster
If you're going to try this yourself, beware of the thumb cluster. In the experience of rianadon, the vertical cluster requires you to press with the pad of your thumb, which places more strain on your fingers than pressing with the side. You can test print just the thumb cluster before going all-in.