Not a patch on the UK government design system IMO. Used by the UK gov and 3rd parties to produce consistent, accessible and aesthetically pleasing public service front-ends. More: https://design-system.service.gov.uk/
Having seen a number of different gov websites, I think that gov.uk are the most aesthetically pleasant and UX-focused. I would only say that at times they are excessively verbose, but that is less of a design system fault and more from the "let's protect us from any liabilities and people making totally silly assumptions about what, when, and how we do things" department.
My favourite part is the NHS website. Pages like this one [0] are an excellent example of clear, effective writing. They heavily influence how I write similar content.
I love the UK government site design, in particular their font (Transport something or other?). Sadly the font may not be used anywhere but .gov.uk sites.
It's called GDS Transport[0] and it's custom version of New Transport (for digital use) that's based on the original Transport font designed in the 1950s.