Yeah this is the explanation I got too, growing up in Northern Ireland in the early 90s you just didn't talk about 'unwed mothers' much so it made sense as a taboo to me, I guess

The Motorola 'moto g' range phones are pretty inexpensive and close to stock android, and the newer ones support esim I believe. My mum uses ones because it's pretty easy for me as a Pixel user to support her but she wouldn't pay Pixel prices.