Current state

• Very much under construction.
• Will start posting thorough design writeup once design nonprofit site goes up.

Compatible keyboards

Keyboards with at least 3x6 and having at least three thumb keys in an arc on thumb cluster. Having a number row is unnecessary, but doesn't have much opportunity cost aside from extra cost, weight, and complexity. Extra thumb keys, assuming they don't interfere much with the ergonomics of the main arc of three keys, are much the same.

• Bastardkb TBK Mini
  • What I recommend most highly. It's essentially perfect, and checks every single box. Everything we want, nothing we don't. Bravo!
• 42-key Corne
  • What I recommend if you want a flat keyboard rather than concave, since it has the exact right number of keys, and lays out the thumb keys in an arc like I find ideal. Concave keywells are superior from a functional perspective (lower finger travel distance), but more expensive/complicated to make (since you can't use flat PCBs), and also harder to transport. I personally think concave keywells are worth the sacrifices, and prioritize superior functionality high above all else, but YMMV.
• Bastardkb Scylla
  • Extra number row
  • Extra thumb keys on each side. If you disagree with my reasoning for only using three large thumb keys (and think there ought to be be more smaller thumb keys that require greater precision to actuate), then this is a good concave keyboard with many such thumb keys.
• MoErgo Glove80
  • Extra number row
  • Extra function row
  • Extra bottom row
  • Extra thumb keys on each side. If you disagree with my reasoning for only using three large thumb keys (and think there ought to be be more smaller thumb keys that require greater precision to actuate), then this is a good concave keyboard with many such thumb keys.
• Dygma Defy
  • Flat (no concave keywells to reduce travel distance). On the one hand, this is not as ideal from a purely functional perspective. On the other hand, it makes transporting it when traveling much easier.
  • Extra number row
  • Extra thumb keys on each side. If you disagree with my reasoning for only using three large thumb keys (and think there ought to be be more smaller thumb keys that require greater precision to actuate), then this is a good flat keyboard with many such thumb keys.
• Bastardkb Dilemma Max
  • Flat (no concave keywells to reduce travel distance). On the one hand, this is not as ideal from a purely functional perspective. On the other hand, it makes transporting it when traveling much easier.
  • Extra number row
  • Extra rotary encoders
• Keyboardio Model 100
  • Flat (no concave keywells to reduce travel distance). On the one hand, this is not as ideal from a purely functional perspective. On the other hand, it makes transporting it when traveling much easier.
  • Extra number row
  • Extra thumb key on each side
  • Gimmicky materials and design (form over function), in my opinion, adding to expense unnecessarily.

Semi-compatible keyboards

These mostly have suboptimal thumb clusters (i.e., some configuration other than having at least three keys in an arc), but could probably work if you wanted them to.

• Kinesis Advantage 360
  • Has three reasonably accessible thumb keys, just not quite ideally arranged
  • Extra number row
  • Extra bottom row
  • Extra thumb keys
• Keeb.io Iris
  • Flat (no concave keywells to reduce travel distance). On the one hand, this is not as ideal from a purely functional perspective. On the other hand, it makes transporting it when traveling much easier.
  • Has three reasonably accessible thumb keys, just not quite ideally arranged
  • Extra number row
  • Extra thumb keys
• ZSA Moonlander
  • Flat (no concave keywells to reduce travel distance). On the one hand, this is not as ideal from a purely functional perspective. On the other hand, it makes transporting it when traveling much easier.
  • Thumb keys are a bit less arc-like than ideal (in a straight line instead). But probably close enough that it would work alright since the keys are larger than 1u, if still not quite ideal.
  • Lots of extra keys