Only way I can think of how to fix it is in its file system, is there a way of getting a SSH on it so I can logging with Putty...?
Then I can fix it, I might be able to copying jst and then renaming it to WHDLoad, then it will use jst but think its WHDLoad, if that does not work then I have to add WHDLoad binary, there is no way of adding WHDLoad to the A600 GS, you can not import it, if you go into a folder with WHDLoad in it, the A600 GS menu Importer can not see it so it does not reconise the file.
If I can not get into it via Putty I can mount its img file using the loop device in WSL(Ubuntu) in Windows 11 then I can then change things on its partition in the img file then copy it back over its SD card but thats a long way round.