I used #Skype a lot years ago. It was our standard chat/voice tool at where I worked and family used it too. It was available on #Linux. I never used the facility to call actual phones much. Now it's being shut down.
https://www.omgubuntu.co.uk/2025/02/skype-hangs-up-for-good-on-may-5
I still refer to a variety of videoconferencing as "Skype" accidentally. Sometimes my students have never heard of it.
Skype looks so old fashioned nowadays, haha!