just wondering – why not package for native iOS or android?
on a side note: i have done no testing for mobile browsers (since they are usually very behind to the desktop browsers.)
because the game engine runs natively on those mobile devices and most browser makers are only supporting bleeding edge features on desktop browsers (e.g. asm.js [back then] and wasm [now]) - there are no plans for bringing UE4 on HTML5 for mobile browsers…
(this may change in the future when wasm becomes supported on mobile browsers – but as of right now, i haven’t heard from apple, google or microsoft doing anything like this for mobile…)