GeckoView doesn't support addons yet. This is pending discussion, but it looks like the goal is to focus on mobile optimization first.
As a tester of Firefox Preview: WebRender has been a godsend for mobile browsing -- I have yet to see it choke!
As a tester of Firefox Preview: WebRender has been a godsend for mobile browsing -- I have yet to see it choke!
Moto G4, Qualcomm Adreno 405, OpenGL ES 3.2
about:config doesn't work either