This is probably a lot more work than you're willing to put in, but the Facebook Messenger bridge for Matrix has actually been reliable, set'n'forget, and headache-free for me, whenever I have to use it for Marketplace.

I wouldn't otherwise mention it, but this is one of the few sites where "Stand up your own messaging server" isn't a completely insane suggestion.

>it's very fractured internationally while being very consistent inside borders

I think it's caused by the network effect [1].

>I for one fucking hate that most of Sweden uses FB Messenger

I agree. Denmark is the same, everybody uses FB Messenger or, even worse, Snapchat.

And don't even get me started on payment systems: Sweden has Swish, Denmark has MobilePay, Italy has Satispay, etc. It's completely fractured and it's so annyoing when travelling across the EU.

At least there's a new European system called Wero [2], I wonder if it's going to help fixing this situation.

[1] https://en.wikipedia.org/wiki/Network_effect

[2] https://wero-wallet.eu/