Right now Firefox OS on ZTE Open is a work in progress. It has tremendous potential, but in case you get one, don't expect the level of polish you get with the popular alternatives. But it's improving and it will get there and if you can, buying one is a good way to support its development.

I would buy Jolla right away if it had a hw keyboard. There may be a FOS device worth buying but I havent seen one yet. I am way overdue for a replacement, and sadly, I need to agree with your parent - there is nothing interesting on the market at the moment.