They can't build one. If they do it would have to be build out of titanium. They'd first have to develop welding technology. They neither have titanium welding tech, nor titanium, nor experience building subs out of titanium. It would be a lot cheaper for them to pay Russians to build a proper sub, about half a billion without support vessel, and about 5 years. Now we all know it's not possible nor it would be possible in the near 10 years. So I reckon it is just a publicity stunt, to get the money, spend that money, and dump the share holders.

No, I meat, it is possible. You just take money, go to Russia, sign contract, pay, have it build, then work on it. But the sub, and the money it makes will be under sanctions. So all the money they make will have to be spend in the rest of the world, China, India, South America, Africa, Oceania, middle East.