So ... I know very little about submarines but what tartare said in #470 is similar to the thinking that I had when the pact was announced - otherwise, why include the UK? If it was going to be US Virginia class, with US tech, then it would likely have been a AUUS alliance. The Astute class makes most sense as that production line nears it's conclusion - hence AUKUS. Plus everyone knew the Virginia prod line is full for the next decade or two.
I also wonder if I've accidentally stumbled on why the French are so 'hissy' about, what is otherwise, a commercial transaction ... you see ... the Astute class have all been named already, even the two yet to be delivered. the 7th (and last British) Astute class is named ... wait for it ... HMS Agincourt!
Perhaps the French are somewhat miffed that the answer to "what comes after Agincourt" is likely to be "Australian Nuclear Powered subs"
[sarc-off] in case anyone was wondering