[kilburn]

This is equivalent to about:config and works on the regular firefox mobile version too:

chrome://geckoview/content/config.xhtml

[cma]

Didn't work for me just now. When there have been ways in the past the non-nightly version wipes the changes each restart unless they are already exposed in settings I think.

[cma]

You have to type it manually and not paste apparently. Mine was already set false so I'm not going to experiment with turning it on.