Like a lot of the comments here, I misunderstood it from the headline

The European Union has recently reached an agreement on a significant competition reform known as the Digital Markets Act (DMA), which will impose strict rules on large tech companies that will have to offer users the ability to communicate with each other using different apps.

I didn’t know this was a thing, what other apps/platforms are affected by this?

Interoperability will allow other people to contact users on WhatsApp even if they don’t have a WhatsApp account. For example, someone from the Signal app could send a message to a WhatsApp user, even without a WhatsApp account.

So it’s about being able to message someone from Signal to Whatsapp. That might be a good thing for Signal/Telegram users, since you always have the option to NOT message someone from those platforms.

What I’m curious about is what data Facebook can collect from a Signal user. I assume Signal will take steps to block third party data harvesting, assuming this even goes through. There’s a similar issue with Threads and other for profit companies joining the fediverse. At least with Signal there isn’t that much data to begin with. I think Fediverse platforms also need some more safeguards on the privacy/security side.