Propulsion isn't the gating factor for submarine adoption. The engineering and precision manufacturing is just extremely difficult all around. For one example there are only a few shipyards in the world with the right equipment and expertise to weld together hull sections. Most countries that want an attack submarine have to buy them used from an ally, or spend $100M+ with one of just a few European or Russian manufacturers. And even once you have a submarine it costs a fortune to maintain and operate safely. Most countries barely use the subs they have because they're in poor condition or lack trained crew.
Full size submarines can recharge their own batteries on the surface using diesel engines. Only some small, short-range submarines rely on other vessels for recharging.
https://www.thedrive.com/the-war-zone/41075/canadian-submari...
Full size submarines can recharge their own batteries on the surface using diesel engines. Only some small, short-range submarines rely on other vessels for recharging.