Regenaxer

If your relative also needs something on Android, you might look at https://software-lab.de/StenoBoard/README

I wrote it when I developed a Dupuytren Contracture on my hand last year, and find it very comfortable and efficient. It is my sole keyboard input now.

No floats, yes, but it has fixnums with infinite precision

The easiest way seems to be to download it with a browser, and then immediately click on "open" in the little dialog which pops up in the browser after it downloaded the zip. It is then passed to PilBox.

Clicking on a Zip in the Downloads app works on some devices, but other systems only offer to extract the files which does not help here.

The 64-bit version of PicoLisp is written in a generic assembler which is then built for target CPUs like x86-64, arm64, ppc64 or "emu". In "emu" the target "CPU" is plain-C, and this is used if the Android device is physically only 32 bit.

Perhaps also the video snippets in this article are helpful:

https://picolisp.com/wiki/?TermuxPentiPicoLisp

I should explain more clearly how to generate an arpeggio in PentiKeyboard:

The rules are: 1. The last key must be pressed AT LEAST 80 ms later than the second. 2. The last key must be pressed MAXIMALLY 240 ms.

A backspace (DEL) is generated with middle and index finger.

While pressing middle and index finger simultaneously (or longer than 240 ms) gives an "l", you get a backspace when you first press the middle finger (as long as you like, but at least 80 ms), then make a short tap with the index finger and immediately release both fingers.

Note that in PilBox you can also directly call the standard Android API, and use the REPL of course.

Taking a picture, for example, needs only

   (android~takePicture (tmp "img")
      '((Intent)
         (... do something with the image) ) )

The function 'takePicture' is in "lib/android.l":

   (de takePicture (Dst Fun)
      (startActivityForResult Fun
         "android.media.action.IMAGE_CAPTURE"
         "output" (fileUri Dst) ) )