I passed my driving test in the early 70s in a manual.
I got my first automatic about 15 years later and have only ever bought automatics since as I much prefer them and would never go back to manual.
However, I would always advise someone to pass their test in a manual.
I suspect we're still a long way from universal ownership of electric cars so the view that all electric cars being automatic is the future, is just that, something that will apply in the future.
As pps have said, automatic cars are always a little more expensive than manuals, so that's a consideration, but having always bought used cars for many years now, I've never ever had difficulty finding good quality automatic cars. I agree though, they are a lot rarer to source than used manuals, so yes, the choice is very limited.
I bough my latest, used, car about 6 months ago and there were very few automatics available.
How your DP has managed to come to his opinion about the matter is a bit puzzling if he doesn't drive. Does he often has strong opinions about thing he knows nothing about?
Make your own decision OP, you're the one that is going to be driving the car, but for what it's worth. I'm another one say go with a manual for your driving test it'll will give you a wider scope when it comes to buying or hiring a car.