Didn't the US government require that all cloud services provided to and by the government be done over IPv4 and IPv6 some time ago?
In opening another tab to answer my own question, I see that they've broadened the scope and that the US government networks should be IPv6-only, with some caveats I'm sure, by 2023: https://fedtechmagazine.com/article/2021/03/how-make-progres...