The visibility of fonts to websites has been restricted to system fonts and language pack fonts in Enhanced Tracking Protection strict mode to mitigate font fingerprinting.

I'm happy to see this. It's crazy how hard advertisers try to determine who I am when I'm actively attempting not to be shown their garbage and won't buy it from their links. Browsers should be sending far fewer html headers, and restricting the listed fonts to a common list is a good step forward.