Should be good to merge, I haven't tested though.

Alright, just tested. The title appears but nothing shows on the actual window.

Alright so adding --start-debugger-server did nothing apparently, I will have to do further investigation

Alright, so it should work with Firefox Nightly, I can't confirm though. If anyone can test, that'd be helpful

Alright, tried with Dev Edition, doesn't work...
But, upon attempting to screenshot something (in headless mode), it... works? This indicates that the problem is somewhere in the code, time to do some more digging.

I did some more digging, I tried using puppeteer-core instead of puppeteer in tests, which couldn't reproduce the problem, I'll try on my desktop later to see if that fixes anything

So I took another look, and it appears to be navigating to networkservice,networkserviceinprocess.com???

Well, turns out that networkserviceinprocess happens to be a flag passed to Firefox, but this raises another question... does Firefox not support this flag? If so, disabling this flag which appears to be there by default could fix our problems

Upgrading to Puppeteer 3 fixed the title, but it still doesn't display

Showing the browser window shows that the weird navigation problem I mentioned here is solved, which is progress I guess?

Using -wait-for-browser allows navigation to work fully, we're getting close!