Lookup PaleMoon and Basilisk in Wikipedia. The codebase of Goanna has diverged from Firefox / Gecko a lot, so trying to compare by versions won't tell you much. PaleMoon Goanna is regularly updated and supports nearly all the feature sets of a modern browser rendering engine and is feature compatible with Firefox / Gecko though it doesn't support webRTC - https://forum.palemoon.org/viewtopic.php?t=28182, DRM and webExtensions ... https://www.palemoon.org/technical.shtml