Levak made an excellent Lua sudoku btw (quite advanced/complex Nspire Lua though) available here :
http://levak.free.fr/ftp/nspire/Sudoku/

I could not find this anywhere on Omnimaga, then realised it probably was on TI Planet. It was.
The .tns file from levak.free.fr works.
But using the sourcecode (.lua) and compiling with Luna I cannot get the code to run at all with
Error: attempt to call global 'PushScreen' (a nil value)

As I do not understand French, posting in English on TI Planet would be quite weird...

I was looking at this topic when I saw the link for Sudoku above.
This is probably totally off topic.

Hmm I see, that would probably be it. I was missing out on all those other files.
Looking at the MakeFile, I can see that it requires MakeTNS.py, which I have downloaded from ticalc.org.
Sudoku.lua isn't in the MakeFile commands...? Oh I see it is, it's at the top as a variable.

This would be the Linux commands more or less:
maketns.py Sudokut.tns Buttons.lua Menu.lua Request.lua Constants.lua ScreenManager.lua Engine.lua Help.lua Sudoku.lua
But since I use Windows, the MakeTNS readme told me to go into the dist folder and execute there
maketns Sudokut.tns Buttons.lua Menu.lua Request.lua Constants.lua ScreenManager.lua Engine.lua Help.lua Sudoku.lua
However it gave me an output of a 10kb tns file where the actual working tns is 13kb. And it wouldn't run on the calculator.

This seems overly complicated. But at least I learnt something.

Oh of course, things were different in OS 3.0.x.
Interesting after manually concatenating all the files into one, I got a file size of 9kb. But it works!
Um, I found a bug almost straight away. If you press the delete key, it crashes.

Well, you should always try to avoid that your script throws errors to the user level (so that you need to catch it with registerErrorHandler). Of course it's not bad to implement it in case that something goes wrong unexpectedly, but still a well designed script should never actually be able to arrive to that point.