I’m using simplex without problems. I get all notifications and didn’t notice an increased battery drain.

It’s technically viable, using a distributed hash table for example. But I’m not aware of any solution that does it.

This link probably will explain it better than me: https://www.engage.hoganlovells.com/knowledgeservices/news/new-guidance-on-cookies-in-spain

Sadly, they are doing it in spain, the judges recently stated that they can do it, and few days later almost all of the spanish newspappers had it.