AudioWorklet (which allows you to work with audio sample-by-sample in a dedicated, high priority "thread") is available and works well in Firefox and the latest Safari. I haven't tried it in Edge, but I believe it's also working well.
As a mobile first web developer, ios is the thing that's really holding us back.
The very frustrating thing about this is that the end user tends to blame the app, and there's not a good way to communicate to them "hey, we would totally do this, but mobile Safari has limited functionality and Apple won't allow other browsers to be installed"