I also had a similar issue with Cascade Bicycle Club - they chose to organize things via WhatsApp, and since I am (inexplicably) banned from opening a Meta account I was completely left out of the group and missed out on many rides/details that were only shared via WhatsApp.

When I tell people that this is even possible I get wide-eyed stares — as if they never contemplated that Meta could exercise their right to ban someone from the platform.

It's a huge problem and I have no idea how to fix it except talk about it and spread awareness. And I am not remotely interested in trying to work around the ban.

You bring up a good point. There is a general lack of awareness of how much power we're giving these monopolists. As a kid, in school I was thought to be weary of drugs, STDs, pimps and other threats. This should be added to the list. Yhis is a clear cut case where governments should start educating the people about this.