The UK previously didn't allow small plug in solar panels (the kind that you just plug in to a mains socket) due to, I believe, safety reasons. This has changed within the last few days https://energysavingtrust.org.uk/solar-roadmap/

I believe it’s only legal in Utah so far in the US: they legislated it last year, and apparently half the country is expected to pass a copy-paste version in their next sessions

It hasn't changed... yet. The media noise is because the government has announced that they were reviewing current rules with the aim of allowing "balcony solar" by the end of the year.