https://css-tricks.com/ is one of the best sources I know of for new and/or obscure stuff in the Web world, including browsers, frameworks, etc. Despite the name it isn't just CSS.
We attempt to do this (as well as the main specs, independent of browser) with our Frontend Focus publication: https://frontendfoc.us/ – however, you can follow each of the key browsers (especially as there are so few of them now!) directly on Twitter or via blogs as ivank has linked here.