@jan @jon, currently all engines are monopolies, depending of big companies. It's by far the most complex part of an browser with a complicate maintance which need a big team of devs.
This is the reason because there are not more engines since almost 20 years, except some marginal forks.
I remember an advice of an browser who anouced awork on a new, independent engine, but this never ocurred and if it is still in work, ther won't be an alpha at least unil 2029.
Don't confuse it, in the wiki you'll find a list with over 100 browsers and another one with almost 70 discontinued.
There isn`t a real alternative to Blink by Google, Gecko by Mozilla (and Google) and WebKit by Apple, apart some irrelevant forks of Blink, Gecko and some indie engines for text only browsers.
The only different one is Konqueror from KDE which use KHTML, the Ancestor from Blink and WebKit. Linux only and pretty limited.
That is the current panorama. Even so, the small Vivaldi team offers the most advanced browser which currently exist.