Earlier quoted context omitted.
I find it funny that if I were to read your comment outside of this website, I could most likely identify it as a HN comment because it mentions barely-used sites popular in HN (such as Bluesky, Signal, Jitsi, IRC, etc), but skips mentioning actually popular ones everywhere else (like Snapchat, Facebook/Messenger, Instagram, TikTok, etc).
Oh, I agree so much, but I am not sure about your examples either: Snapchat - does it even exist anymore? It had its time, but personally I don't know anyone still there. Same with Facebook Messenger, which has completely been replaced by WhatsApp in my (non-nerd) circles. I thought about including TikTok but it would be more in the - YouTube, TikTok, Vimeo, PeerTube category. To me, these are borderline social media…
None of the other ones that you listed are popular in the US either with the exception of Twitter, Zoom and Slack (and the latter two aren't social media platforms).