MediaSourceExtensions (https://caniuse.com/mediasource)is one good example of a useful API which has been supported by roughly ~every browser for years except for safari on iPhone.
On that page it says that media source was implemented in 2014, on year before Firefox and Edge.
I guess in your world "every other browser" is Chrome. And, sure enough, there are some parts of the API that are only implemented by Chromium-only browsers, and are not implemented by either Safari or Firefox.
