Fittingly, just two days ago they did open up a Mastodon account — this one: https://hachyderm.io/@guix. I'd say be sure to boost their initial toot and possibly more.
From an email that just appeared on the devel list:
Hi,
As you will have seen GNU Guix is now on Mastodon - we have entered the social media age: https://hachyderm.io/@guix
The goal of being on Mastodon is it's another communications method (like the blog an email lists) that we can tell people about GNU Guix, but also engage with people about Guix and related topics.
It would be great to have a few people who'd like to regularly post and engage. Anyone interested?
..
There's a monthly Nix meetup in my area, "Nix your bugs". Never been there. I'm currently contemplating showing up there with my NixOS laptop and nix all the bugs (well, replacing them with others) by installing Guix. Given the recent developments, I don't even think most of the people who are there will consider that a dick move.