As a reply but also as a general post to help everyone who uses Discord
Having the DISCORD game overlay working while playing a game can be very useful, but.. not all games are supported and even when a game is supported, it can sometimes be a pain.
In case of Elite:Dangerous, it helps running the game in full screen with borderless windows
Make use to enable the game overlay for Elite:Dangerous in Discord
It is possible that next time when you start Discord and/or Elite:Dangerous, you'll have to do this again!
(not sure why.. maybe it's the game, maybe Discord, maybe both..)
And yes, there's also "a master switch" for the Discord overlay, don't forget to turn this on
<deja vu> It is possible that next time when you start Discord and/or Elite:Dangerous, you'll have to do this again!
If you succeed, you'll see this in the top left of your screen
"See" you on the MOBIUS Discord!