I wanted to join a Discord that required phone number verification. I gave them the number I've had for the last 24 years, and they said it was invalid because it is hosted on Google Voice. I asked for alternative authentication and they said, and I quote,

"Do you have a friend who doesn't use Discord? Can you just use their phone to verify yourself?".

Since then I've been very anti-Discord (but will still occasionally pop on because there are some interesting communities there).