The AUKUS agreement effectively removes the legal taboo of the US or UK exporting 93+% weapons grade nuclear reactor HEU to Australia. By this taboo removal this trends toward legitimizing nuclear submarine propulsion for South Korea.
For years and as recently as late August 29, 2021 South Korea has been raising the idea of nuclear propelled South Korean subs.
In November 2017 South Korea's President raised the idea with President Trump of South Korea purchasing a US nuclear propelled attack submarine (SSN).
Also see further references to nuclear propelled South Korean subs called "KSS-Ns" here.