>>tikkun+hj
Skype became really really terrible, it looks like it's been unmaintained during the past 10 years, I'd rate its usability worse than most open-source software. The sound quality is also awful, it feels like I'm calling a landline.
>>gumby+Ft
In the US I don't know a single person that has access to POTS. Discord (with paid nitro) is the gold standard for quality and latency, followed by all the free VoIP apps
>>NavinF+PT
I live in the US, and I'm pretty sure everyone I know has a landline, though a good number of them are now digital/fiber/whatever. Some people I know still have multiple landlines, as it's cheaper than paying multiple cell bills if necessary. I know at least one person who used to have call forwarding set up to get calls on their cellphone, but with the current state of marketing calls they probably don't do that anymore.