They've moved to ma(th)stodon after the twitter clusterfuck: https://mathstodon.xyz/@nbourbaki

> which canonically is run by the daughter of Nicolas

Is there a joke I'm missing?

Nicholas Bourbaki is not a person. The Bourbaki group are a collective who work together (at a glacial pace) and publish under the pseudonym "Nicholas Bourbaki" when everyone in the group agrees that the work is done. They have lots of "in jokes" not least of which is the name Nicolas Bourbaki itself. Another of these in jokes that Nicolas has a daughter called Betty. They apparently published a wedding notice for her at some point also.