Finally the problem was the fact that I was using PHP v8. I used a lower version and all worked fine!
Thanks for the help!
I only have limited IIS access via the web-based control panel available by my hosting provider, so I don’t have access to the Web Platform Installer.
I did everything in the second link you provided and get the error at step 3 of “Setup and Configure the Application”.
I have opened a ticket with my hosting provider to see if there is something they can do on their end.
