I'm using a Nokia 2720 Flip (https://phonesstorekenya.com/wp-content/uploads/2020/02/Noki...), a phone from a line of those old-time phones: big physical buttons, 4 directional keys. It runs KaiOS (https://en.wikipedia.org/wiki/KaiOS) a recent OS that targets low-end "dumbphones" but still gives them modern functionalities. Most are unneeded in the context of the thread (Facebook, Ok Google) but some might be useful (there's Whatsapp if you really need it, emails)
There's a list of devices that are sold with it in the wiki page. It's primarily targeted at emergent markets but you definitely can buy them. Bonus: because they're simple, they're cheaper