My friends and I are hosting a Linux and FOSS group chat to have some casual chat, help, and anything related to the topic really. We chose this platform to chat on to keep a privacy preserving way to engage with one another.
https://signal.group/#CjQKIBshKeuikl5HfagdB46bXpGOyQf_4cVvO3vUMs71DiB9EhDEbE8mS3EPYL0e9CQWHBsy
I mean like 10k+ users by “mass audience,” ala Telegram. As far as I am aware, nothing will do a channel that large and actually encrypt e2e.