I _really_ liked the "hangout" idea of Google+. Where you could just start a video call and whoever among your friends wanted to join, could, without having to accept or reject an actual invitation to them specifically. I could work on a project out in the garage and people could hop in and make small talk while I was doing stuff. It was great.
It doesn't feel like there is a great modern alternative to this.
Yep, this is the exact use case that voice channels are used for in the community-oriented Discord servers I'm in. With the important note that voice channels support not just voice but video, multi-person screensharing, text chat, and even built-in games, though I've never actually seen the last of those get used in practice. Voice channels are just passively there in the channel sidebar with a list of people currently hanging out there, and you can drop in and drop out as you like. You can also send individual invites to join you in VC to server members.
Funny story -- one of the first few days of the internal launch, a colleague didn't know what the feature was and clicked it on Sergey's page one night. Suddenly was face to face with Sergey at home. And he wasn't the only one, from what I remember.
I like Signal a lot. I would much rather use Signal than Discord, or :::shudder: Facebook (because in SE Asia a lot of people think that's the internet).
In the days before Mastodon it was the geek/nerd social network of choice, and the majority of all the people I knew in the Linux and FOSS world were active on G+.
Yeah. I know zero people from HN or, say, Reddit, and even from the tech/coding world (and past workplaces; not that they were a Signal weilding crowd even by a stretch). I have friends I can count on the fingers of one hand, at most both hands. I will never have to reach for the toes :) So if that's the opposite for you, then it might be the case. Or, honestly, even if that's not the case, it might be so. And since I don't have empirical research other than what I see "around me," I can't just say that's how it is "generally," even though that's exactly what I see :D
(PS. There was a time when WhatsApp ended up having really bad press a few years ago and I was abl to make almost 30-40 of my contacts to Signal but Sigal being Signal and its team/leadership successfully pushed them all away, a lot were crashes and what not. Even I was frustrated. It was the first time I was "using" Signal beyond "trying" it which is like an annual or half-yearly ritual now)
This is Discord for many folks. You have voice/video channels alongside your text chats. Anyone can hop on into any themed voice/video channel at any time with the added bonus of screen-sharing game content.
It doesn't feel like there is a great modern alternative to this.