[2023] Paradox Launcher crashes my Internet (3.9)

Game patches do not in general mean launcher patches or updates, they are separate apps.

So was this perhaps after a launcher update? 2023.11 came out a couple of weeks ago.

That said, I have no idea what the interaction between it and your internet connection could possibly be. Make sure all these apps are in the exceptions lists of the firewalls in Windows and in your router:

dowser.exe (in the Steam Stellaris folder)
C:/users/{username}/AppData/Local/Programs/Paradox Interactive/launcher-v2.2023.11/paradox launcher.exe
C:/users/{username}/AppData/Local/Programs/Paradox Interactive/bootstrapper-v2.exe

Does that help?  

I don't know, I'm sorry! Never needed that info in the years the launcher has been out ...

The url it goes to is https://api.paradox-interactive.com if that's of any help.  

If you have a VPN, try logging into that before starting the launcher/game. Does that change matters?