I expect down the line that this is inevitable, perhaps an easy config or setup to add additional dispays and control how they are handled.
But I am sure there is quite a lot of us looking forward to using dual monitor functionality. Just a matter of time and interest to build.
Is the setting "Disable other displays" enabled or disabled?
Cloning should be possible (both screens having an identical resolution), it's the only mode that Kodi supports.
Dual screens work on Raspbian Buster on a RPi4 here, so technically it's possible.
I'm waiting for a delivery of micro HDMI cables, currently I only have adapters that are too big to put two in at a time. Will report on whether or not it works.
I had to file off a bit off my HDMI cable plugs to have a decent fit. Most micro HDMI plugs are still a bit clunky.
Ok, I got way more cables than I ordered.(6x) micro hdmi to hdmi.
I'm having the same problem as OP. It shows the rainbow test screen but doesn't show a clone.
Hello all and thanks to the Devs from a Newb 
Ran into the same issue on a fresh install yesterday, haven´t found a clone-option somewhere in Kodi... is there maybe a fix for that in librelec configs?
"Disable other screen" isn´t ticked, works generally since it IS showing the rainbow, but no kodi on display 2 
I doubt this will be implemented. The main reason, is that Kodi is a media centre - and who has 2 TV's next to each other in their living room? Also, what would be the point is having the same display split over 2 screens? I can see there *might* be a use for expanding the display across 2 screens but the resolution would be atrocious and barely watchable.
Lot easier to buy a larger TV 
Fair point, though i really have scenario one screen at the desk for having some background noise while working, gaming etc, one at the bed for watching series and such on a more comfortable base. for me it would be mirroring, not stretching/expanding.
I was just thinking something might have come up since the last post since the 4 is longer around now.
Thanks for the feedback, though. Running on an hdmi splitter atm, might as well get another raspi and quit whining
Ok - That's a good enough scenario to give it some credence. It might still be possible. I don't have duel displays so can't test any scenario.
RPi4 hardware supports dual outputs (up to 4k@30, using 4k@60 means a single output) but your ability to use this depends on the OS supporting it, and then applications in the OS being able to use the screens. You can maybe force mirroring in RPi4 firmware via config.txt but LE itself provides no options for configuring anything within the booted OS; and Kodi has no support for dual-screens.
Good one, thank you. Tried that from the raspi forum
# Test Screen Mirroring
max_framebuffers=2
xrandr --output <HDMI-2> --same-as <HDMI-1>
and it kind of changed something. the rainbow is gone, now the second screen is black
Don´t have much of a clue what i´m doing here but will investigate further when having time.
Kodi has some controls for sending a second screen to black or .. I forget because I haven't ever used them. The original purpose is to turn off a laptop screen when the GPU mirrors content to screen + external port. It may or may-not be a relevant hint. The target of the feature is normal desktop OS that run on laptops. LE somewhat deliberately doesn't fit the definition of either so YMMV.
Guess you´re right, all I did was hitting sth by accident.
As far as I understood from further googling around I´d basically be best off using a less compact OS and install kodi there... I will do the reasonable and get another raspi with libreelec, who knows, that might offer synergies.
Thanks for your Time and patience, Guys
What's the value of it? Literally playback of 2 different things to different displays around the house? (Pi 4 might be able to do that at 1080p?)
I think maybe more likely a clone display might be useful?
Indeed, clone display with the 2xhdmi of the pi4 was what I was originally looking for and what is currently in use with the help of an hdmi splitter.
Might as well just stick with that (getting libreelec to use clone mode seems to exceed my knowledge by far and i don´t want to switch to some other os) or do what a reasonable hipster should do and just get another pi
Moin,
I'm new on this platform. The reason to subscribe were these two points:
1) I would say thank you for all the Kodi and Libreelec stuff!! I use Kodi since some days (on a rasp pi 4) that's mostly great! 
2) But: One of the things I am missing is the second display!
I'm a bit surprised that you more or less see no need for that!
I think every media center / player / etc. should have a (touch) display to operate it without TV. Every DVD player have a display!! So I think it is OBVIOUS that such a second display makes some sense!
I would prefer to have a small touchscreen for the Kodi GUI and (of course) the TV as the second for the video/movie stuff!
If I hear radio or MP3, I would control the raspi with that (always on) panel. I know I can use my tablet (an I do) but I think such a small touch display would make "a real", easy to use "product" out of my nerdy media center!
The second display could be configurable:
1) always mirror the first
2) always Kodi GUI
3) off
4) expand?
So, I felt a real need to add that here!
Cheers
Kaktus
Just use a tablet or phone with the kodi remote. You can browse your media and select content from there.
