Perhaps like USWDS? https://designsystem.digital.gov/

It definitely looks like USWDS, which happens to have accessibility well baked in.

It has been years since i have had to manage web design stuff...but as i recall, section 508 specifically calls for federal-centric web properties to - by law - include accessibility features to accomodate the American Disabilities Act (the ADA). So, yeah, it better damn well have accessibility baked in, else it would be illegal. :-)

To be fair, the little documentation and blog posts here and there that i have read on the US Digital Service is that those folks reaslly are attentive to design considerations for always including accessbility...which is awesome!!

This site uses the USWDS

The UK has https://www.gov.uk/service-toolkit and https://design-system.service.gov.uk/

I wonder if what they meant was "it's impossible to have a turnkey solution for UX"?

There are all sorts of turnkey solutions for frontend and backend infrastructure, but none guarantee good user experiences - only a team that knows their users' needs and is empowered to meet them can do that.

Yes, this is exactly what I meant to write, but stated less clearly than you did. Thanks.