I am impressed at the amount of downvotes. The US had crossed several thresholds now which would've (and should've) caused Civil wars a while ago or in other countries.
Downvoting the post above confirms it has not yet been understood where the US now stands.
Depends on the location I guess. Here it's mostly done and since it doesn't really take any effort I would agree a look behind and holding the door is something everyone should do.
FYI this is one of the main differences between the Hollywood and German soundtracks.
Here it's mixed far better to listen in stereo while in surround cinematic you need to turn the front speaker up, if you have that system. And it doesn't translate well to stereo.
Well then, literally almost ANY chat daemon you can install in any Linux will just do. And there are loads!
If you want to pay a provider to do that or rent a cheap Vs and do it yourself is another thing.
So if some guidance is all you need that's fine and something I'll gladly provide. Rocketchat - as someone else already posted - is relatively recent but also quite modern due to this, running in browser, app or mobile (but quite the overkill für a handful of people).
Any really old IRC based daemon would not require any resources by today's standards and still run perfectly for your case. But it's very old standards might not fit your expectations.
This question is so generic with added weird statements, there are literally dozens of solutions with little research. Due to this I assume you haven't formulated all your requirements and want us to get them out of you.
And again, as usual, advantages if sailing the high seas.