From here:
display_rotate isn't designed for the LCD, doesn't adjust touchscreen coordinates, and will also affect the HDMI display if you try to use both displays, so should be avoided if possible.I think what the correct display orientation is will be something not everyone will agree on. However if you prefer the other orientation then lcd_rotate=2 is the solution.
I think you should try lcd_rotate=2 instead of display_rotate=2.
Get yourself proper internet connection? 
You can download image directly on LibreELEC download page - but it is little hidden.
LibreELEC-imx6.arm-7.0.2.img.gz
LibreELEC-imx6.arm-7.90.008.img.gz
I got it working just few minutes ago, by running the script (spotify-script.sh in my first post) from autostart.sh.
Script you posted has error so I don't know how can it work 
- you have
ExecStart=
inside.
service.spotify-connect-web is already a service by default and should start automatically.
What you get with command
systemctl status service.spotify-connect-webIf there is no LABEL run then this will not work for you - it was added not long time back.
No idea for your second question - don't have any UEFI capable system.
I don't know what happen but you can avoid creating second USB stick.
After first one is created with Creator tool open file syslinux.cfg. There is a line
DEFAULT installer
change that to
DEFAULT run
Also change file in EFI folder. After you will boot from this stick it will be just like installed (and you would avoid one step).
Please give me a hint how to correct this. Is this a problem of settings or of the build?
Maybe this issue will be resolved by itself in next builds because no one around here can fix it. And it is probably the build itself not the settings.
I see no reason why would fail then. And you don't need to use sudo - the point of all those changes were exactly that 
Sadly I can't really help much anymore. If you could provide remote access then maybe I could try something and see with my own eyes what is going on 
The tool "populatefs" does refuse to open part2.ext4
The file is there and I was able to mount it to some folder. I think the problem might be in populatefs.
File permissions are ok?
CodeError: [Filesystem error] /tmp/tmp.7W2JyYfMyC/part2.ext4 cannot be opened.
This same error was reported not long back. No idea why it happens. That's why you will need to debug it yourself - put some echo's and ls in scripts/mkimage to see why it happens.
There is a known problem with this particular version of gcc.
Which problem exactly?
We don't have any build issue with 7.0.2.
Sorry I don't understand
Same here 
Sorry TVPL but I don't know what kind of display is this.
But because RPi is using sd card for libreelec it very easy to test
7.90.003 doesn't include any extra imx6 patch. Because of that some functionality seems better (like in your case) but other were worst.
7.90.005 includes only small changes to upstream kodi (to even compile it for imx6). Nothing else. If you have an issue with this version it is a problem with some upstream commits mk01 did. But because no one has any contact with him there is not much hope for a fix.
Try
kodi-send -a "PlayMedia(/path/to/movie.mkv)"
What is a the correct phrase?
I think XN,C to Kodi. But I don't see error in transifex?
7.90.004 image build. This one is still using huge patch based on xbian's kodi which includes more changes to kodi. In 005 I didn't do that anymore because it is hard to get this working. Maybe I should look this again... That's why images from 005 on are using only original kodi + some small patches.
escalade, you are correct: enabling autoreconf should fix this issue because I don't see warning anymore with my patch. Seems this should be done for some other packages too (I noticed warnings with libressl, glib, libX11, libdrm, alsa-lib, and few others).
And yes, this patch will be PR-ed. First I need to build all projects to confirm they at least build.