(a) The reason we don't have submersible aircraft carriers is not lack of funding, but because actual submersible aircraft carriers are a bad idea. (It was tried)

(b) The idea that submarine tech is underfunded is...interesting.

(c) If you consider that the main purpose of an aircraft carrier is force-projection onto land via the air, I'd argue that the modified Ohio class subs discussed in the article, with room for 154 land attack cruise missiles, 60 special forces and drones, could probably count. So we do have that equivalent.

If you check the operational history of the Japanese I-400, I think you will see that it matches those current capabilities quite well https://en.wikipedia.org/wiki/I-400-class_submarine#Operatio...

And coming back to point (a), the short-term force projection possible with a submergible aircraft carrier would be considerably less, and long-term operations would negate the advantages of being submergible.

(d) The other purpose of aircraft carriers is "showing the flag" (visibly), and for this submerged aircraft carriers are somewhat unsuitable...