I reverted to FF 60 ESR now.
It still has the media emulate feature and won’t bug me every other day with new update installations.
Hi guys, any news on this?
This feature is really VERY important - signing the petition now 
Thanks all for the input. We’re working on this now 
Which version is needed for this? Just installed “Version 68.0a1 (2019-04-08) (64-bit)” using firefox-trunk from the ubuntu-mozilla-daily ppa and I’m not seeing that icon.
Edit: Works in 68.0a1 (2019-04-10) (64-bit), thanks!
Though Firefox version v70+ has the option to “Toggle print media simulation for the page” (as seen in the GIF by @pbro), there seems to be no way to do the opposite—disable print stylesheets while printing.
This used to be possible in Firefox with media emulate screen, and is supported in Chrome by selecting screen instead of print in Chrome Devtools (https://developers.google.com/web/tools/chrome-devtools/css/print-preview). It’s immensely useful when printing those web pages which only have screen-specific stylesheets, and thus appear broken when printed.
Is this feature in the works? 
No this is not currently in the works. We have the capability to do it, but I don’t know where such a feature would fit… The command line was a good place for it, but that’s gone.
I wish we had a command menu like Chrome, that would make it easy to put all of these actions that otherwise don’t belong in the UI.