I have had problems getting Skype to work on my old 1.2 GHz computer.
Every time I try a Skype Out call using the dialer, the whole system freezed up. I tried lots of things upgrading kernel, new versions of Alsa tools etc, thinking it was a sound problem.
One of the few remaining options was eventually the graphics driver.
I had used the nvidia drivers on this machine. Since this machine has a very old nvidia card, I had to use 71.86.07 version, i.e. the oldest legacy drivers (I think there is a newer one out in this legacy series now that I haven't tried).
Anyway, I switch over to use the open source (xorg NV driver) instead.
Surprisingly, no more freezes Skype (v18.104.22.168) working perfectly.