For those just now encountering isomorphic keyboards, my experience with them is purely in software on a tablet, courtesy of a pair of extremely tangential links that I encountered a while back. While esoteric, they're what have made me wish that I was wealthy enough to get a physical isomorphic panel for a hobby — but as a non-pro and student, it's not yet time, so software it is. There are various websites and apps that implement them — either isomorphic or microtonal + either keyboard or midi should locate them for whatever platform is of interest. And then, for two things completely tangential:

Physicists may particularly appreciate that someone made a distorted isomorphic keyboard layout that implements 5-limit just intervals and it ends up being a quasicrystal. While not a true isomorphic, it certainly draws connections that I don't otherwise get to talk about on HN much, and if one were to take the 7-JI 3-D quasicrystal and combine it with a webcam theremin, I'm sure the results would be entertaining. https://old.reddit.com/r/microtonal/comments/1l1m0e6/quasiis...

Caftaphata is one woman's ten year project to create a conlang ('constructed language') that converts human mandibular positions into 5-D chords and builds a tetris-block language of phonetic rules out of them. There are maybe twenty videos posted so far presenting each stage of the grammar and construction patterns. Each chord is a word constructed by plain rules. Studying these videos since they launched a year ago is what led me to learn about isomorphic keyboards. The accompanying instructional videos also have the distinction of being narrated fully in Lisatopian (the creator's first conlang), so not only sound but also subtitles end up being required. This is the Caftaphata intro video; 5 minutes, sound is mandatory and may feel dissonant at times: https://youtu.be/cMnuMjXeHrY

Terpstra Keyboard