It's such an odd problem from my perspective as someone who doesn't live in a western country! We still have 2G on all carriers and seemingly no plans to shut it down. So, if you want to use an old (GSM) phone, it's a non-issue, you just pop your modern SIM card into it and it just works :)
In my country (Poland) a bunch of networks recently switched off 3G and a lot of 4G services in favour of LTE only... A pretty good mobile service I enjoyed at my country home for over a decade had suddenly turned to crap... (at least I have faster Internet access now, but I can't strap a directional antenna to a mobile phone).
