I was recently looking for a PC-to-PC only text chat program to use between my computer and my wife's. We text using iMessage otherwise. Part of the requirement was to be able to see when the other person was online/away. The latest Skype is terrible, along with basically every other Windows10 chat program available today. I can't tell if companies are trying to hide when their contacts are online/offline in order to…
You might find Telegram incredibly useful for what you describe.
I don't know if these modern messaging apps are using the same framework or what, but Skype/Telegram and whatever else I tried seem almost identical. I took away the idea that they were trying to encourage usage and engagement by not letting you know when someone had shut off their machine or not. Like a push to always be connected, install the mobile app and then not worry about ever being away..
that concept doesn't work for me because my phone has nothing but SMS/iMessage and calls enabled. I am trying out two more options though, since I'm always looking for better privacy/encryption.
Retroshare & qTox are two that I'm currently testing. I'm not entirely happy with Trillian's encryption (nonexistent).