Great example. No, they didn't, though you wouldn't guess that from the news coverage. They filed complaints with four regulators. The details are all here. https://noyb.eu/

Why does your link list maximum fines in millions why other links say billions?

"Three complaints worth €3.9 billion were filed in the early hours of Friday morning against Facebook and two subsidiaries, WhatsApp and Instagram via data regulators in Austria, Belgium and Hamburg. Another complaint worth €3.7 billion was filed with French data protection authority France CNIL in the case of Google’s Android operating system for smartphones." https://www.irishtimes.com/business/technology/max-schrems-f...

edit: To me, the difference between 'suing' and 'complaints' seems unimportant if the potentials fines from a 'complaint' could be so high.

The difference is that if you sue someone, they will by definition face legal action. A complaint is just a tip-off. In only a tiny minority of cases will there be any action, and most of those will be a warning letter. Admittedly these cases in the link are very likely to be investigated, but they would have probably been even without the complaint. Apart from anything, the ICO in the UK is already investigating Facebook because of Cambridge Analytica.

"Mrd" is short for billion, seems like they missed that while translating it.