A cross-posting from K-Meleon forum (since their forum connection is a bit strange at the moment): Re: Using the Goanna engine instead of Gecko in K-Meleon...
Posted by: roytam1
Date: November 28, 2017 11:59PM With applying mozilla.patch by hand over palemoon git rev 6bb8c4459(with my XP patch set), and some hacks over generated goanna include files, a test binary is built. 

Drop contents of lav.7z in where k-meleon.exe lives for enabling ffmpeg decoder.

spellchecker kplugin can't be built because of conflicting uses of nsString internal/external APIs from unknown include file(not fully checked all include files). EDIT: spellchecker can be built now! EDIT2: There are some known bugs:
- In about:preferences page, List is empty in Application page.
- In about:preferences page, Content page is not working.
* EDIT: adding these in prefs.js making them working again:
user_pref("pdfjs.disabled", true);
user_pref("browser.eme.ui.enabled", false);
user_pref("browser.translation.ui.show", false);
user_pref("browser.search.showOneOffButtons", false);

- View Source window: charset menu and find bar not working
  EDIT3: about:config flags:
- for disabling async MSE: media.mediasource.format-reader=false
- for enabling VP9 MSE: media.mediasource.webm.enabled=true
- for enabling Firefox compatibility: general.useragent.compatMode=2