[jfk13]

Firefox has had MathML support for a long time. Complain to Apple and Google (and vote with your browsing activity, by using the browser that is less driven by commercial considerations).

[realityking]

Safari has supported MathML since 2011. Though apparently the implementation is somewhat buggy.

The real issue is the lack of MathML support by Chrome (and until recently, Edge)

[extra88]

Yes, Chrome had some MathML support but removed it (I think as part of their forking of Blink from WebKit).