Signal seems to be getting along just fine, despite not collecting advertising data from users about our messaging habits.

And if they want to run a free messaging service supported by advertising, there's plenty of ways to do that which are in compliance with the GDPR. For example, they could start by being really clear about what data is collected in their privacy policy and for what purposes. They could stop collecting data and just have worse advertising targeting. And so on.

But instead of any of that, they're actively choosing to break the law and now crying foul when the government takes them to task over it. Boo hoo. European countries have the right to make laws protecting their own citizens' data. Facebook isn't a country unto itself.