MS GitHub doesn’t do anything the others can’t besides the social media features which do not need to be so prominent. If you must, it can be one of multiple code mirrors but should not be the exclusive one, or even the primary option.

Matrix is ass. You cannot reasonably scale an eventual consistency model without centralization & it will be a wasteful network like many of the blockchain projects. We already have had IRC & XMPP MUCs for ages that run on toasters & did not need to be reinvented. Chat has its place tho to help steer folks into asking the right questions, but such questions once formed need to be triaged as bugfixes, issues, FAQs, or forum posts to benefit everyone on the discussion.