HN is social media. So there.
And this is why I no longer use any Meta products.
What I can do is help my family and friends understand the choices they are making (e.g. use Signal to talk to me). That rush they feel posting something has effects on people in their graph and now they at least understand that and pause.
Another example is ancestor "research" type sites, or DNA tests to find "your true ancestry". I had no choice a cousin of mine chose that as a hobby.
All of those services you list are examples of an online medium that exists for the purpose of socializing. So yes, they're all forms of social media, even if they're considerably less structurally harmful than something like Facebook.