I have tried a lot of technologies & chose the ones I like for on their own merits without following ‘trends’ as they should be used more.
Darcs predates Git & does a lot of things better than Git (plus I want to dog food supporting it); Pijul does great things too! If Nixpkgs has fetchers + prefetchers, there should be a tool that can support users not supported by the builtins (which is only URLs, archives, Git, & Mercurial). Hopefully we can get the Fossil prefetch script merged too for support. Supporting these alternatives is a part of the premise. Flakes can never support this—& they do not seem to want to accept any fetchers despite a few attempts due to the maintenance burden.
XMPP is a reliable, lightweight, decentralized messaging platform commonly, but not exclusively, used for chat. It offers more features than IRC & runs using 10x less resources compared to something like Matrix so I can in good faith recommend self-hosting your own node. I would like to set up an IRC gateway that works at some point, & if ProcessOne adds fuller gateway support to Ejabberd for the MUC, I will enable it despite not caring for Matrix. There definitely isn’t going to be any Discord option.