Google has extended 4K streaming in Stadia to the Chrome browser for PCs.
It has also added the Web Capture LIbrary, for access to captured screenshots and clips on a laptop or desktop computer. You can also now download them to your PC or Mac.
There is a caveat for 4K streaming through the browser; you will need the required hardware for it to work.
Not only will you need an internet connection with speeds of at least 35Mbps, you need a computer that supports VP9 hardware decoding. And a 4K monitor, of course.