Ask HN: Are Facebook-driven sales incompatible with GDPR?

As far as I know, the only "official" way of tracking Facebook sales is their "pixel". Unfortunately, Facebook has a habit of using the data collected by those JS snippets for its own profit. If I understand it right, every single Facebook ad client under GDPR must provide:

- an explicit opt-in for any tracking, including Facebook's (so the pixel can't be included on a page until user gives their consent)

- the opt-in message must be clear that the data will not only be used by the business, but also by Facebook for… what exactly? (looks like it's impossible to even state that message because Facebook doesn't tell anyone how they use user data)

- user must be able to cancel that opt-in and all their data must be removed. It's impossible to initiate that process being Facebook's ad client

I wasn't able to find a single word from Facebook on this issue. Starting this spring it becomes illegal to use Facebook to track ads. Has Facebook really left its EU customers hanging?