Good morning, Maru.
I hope this is a joke, but the only way to exit the Windows Beta Dev Insider program, as you indicated, is to REINSTALL A CLEAN VERSION OF WINDOWS. This means losing all my programs, settings, and everything else. This is what it tells me when I try to leave the Insider program.
Now, I don't want to go crazy, but for heaven's sake, can you evaluate the consequences of what you suggest and inform yourselves before offering random solutions just because someone wrote it on a forum? I'm literally getting angry about this. I have software with customizations, etc., and now I have to reinstall everything from scratch, losing even the libraries that are internal to the programs?!
I can't exit until the next release of a beta version of Insider, nor can I roll back to the previous version as it immediately installs the Insider one since "YOU CAN ONLY EXIT IF THERE'S A NEW VERSION" ... thanks for the damage! Your programmers, testers, problem solvers didn't know this???? If that's the case, I believe there is little hope that you can fix compatibility issues! Now I'm even furious.. thanks a lot!
And it's my fault for trusting and solutions blindly.
For all users: NEVER INSTALL THE INSIDER VERSION!!! AVOID IT AT ALL COSTS!