Hi @ben.boeckel! Thank you for the reply.
The version I have installed is an official one.
Just to clarify, CMake works correctly on my machine. The error above occurs only when, on the same system, I try to access CMake from a terminal opened in Eclipse Theia, after starting the application from an AppImage file. CMake works correctly in Theia as well, when the application is started from the source code, so this led me to believe that something is not correctly set up when the app is packaged in an AppImage file.
However, the PATH appears to be set up correctly and I could find no obvious reasons as to why the error is occurring. I was hoping that somebody might have any pointers at what else could be wrong in the app environment.