Sadly it can’t work that way. From a programming perspective alone they are very different engines.

Unity uses C# while Unreal is C++.

There are also used units like the Pioneer XDP-100 which is still good, but the Android bit is slow.

Now you can go into pretty much any thrift store and get a whole box of them for like $5-10.

Not that Mozilla has been 100% great either. Remember the Mr. Robot debacle?

If not: https://www.theverge.com/2017/12/16/16784628/mozilla-mr-robot-arg-plugin-firefox-looking-glass