People put one or many links to their accounts. Unless there is a email or an actual social media, it is very hard to pick one of these as a way of connecting people.
For example I saw a lot of accounts with just github (same goes with some of the social medias), I am not sure what to do outside of following it. I would assume there is also a understandable inertia to put your own social account or email directly here.
> Any more ideas about that?
Email-chain would be the easiest. I wouldn't rely on a third party service like Telegram or Signal directly as that would mean losing a lot of people because as you realised it is hard to convince everyone to agree on Apples to Oranges.
One thing that could also work is creating a some form of very simple forum board like interface on the website directly for people to post/comment their invitation/willingness to meet up or how they wish to be contacted about meeting up (maybe with a bit information about what they expect or what you can expect).
It could function like a Facebook Group in a way which served a similar purpose in past.
There could also be a Country/Nation board that will also share same posts as your city so more people can see them. If you would like to discuss in more detail, you can send me a email.