Is there a federated and/or self-hosted alternative to Signal with similar privacy and security properties? Even if it supports fewer platforms? I've been getting more and more interested in running my own (and perhaps my friends') infrastructure, but I haven't found anything better than IRC for chat.
> "but I haven't found anything better than IRC for chat" If IRC was your best bet so far, you might want to have a look at good ol' XMPP aka Jabber. If you're into Android, with Conversations [0] there's a suitable client which supports end-to-end encryption. For other OS there are many other choices with different encryption options. While OTR (Off-The-Record Messaging) might be the most popular one, it unfortunate…
It's XMPP with everything you'd expect. Inline image, videos, presence, everything.
(if you cannot buy it, you can get it for free from FDroid but really, buy it!)