I wanted to try steamlink without reinstalling anything, so after about an hour of screwing around here is how I got it working.
This only makes changes within /storage/steamlink , nothing else is touched. If you do not have at least a novice understanding of linux shell or don't fully understand the commands here DO NOT ATTEMPT.
First thing we download the newest Steamlink and extract it (run on rpi)
cd /storage
wget "$(wget -q -O - http://media.steampowered.com/steamlink/rpi/public_build.txt)"
tar -zxf steamlink-rpi3-1.1.28.72.tar.gz
Next we need to download the missing libs that aren't included in this or libreelec itself. These commands might work within the rpi itself but I did them on my desktop.
curl --header 'Host: director.downloads.raspberrypi.org' --user-agent 'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:63.0) Gecko/20100101 Firefox/63.0' --header 'Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8' --header 'Accept-Language: en-US,en;q=0.5' --header 'DNT: 1' --header 'Upgrade-Insecure-Requests: 1' 'http://director.downloads.raspberrypi.org/raspbian_full/images/raspbian_full-2018-11-15/2018-11-13-raspbian-stretch-full.zip' --output '2018-11-13-raspbian-stretch-full.zip'
unzip 2018-11-13-raspbian-stretch-full.zip
rm -f 2018-11-13-raspbian-stretch-full.zip
mkdir x
mount -o loop,ro,offset=50331648 -t ext4 2018-11-13-raspbian-stretch-full.img x
cd x
for i in libpng16.so.16 libicui18n.so.57 libicuuc.so.57 libicudata.so.57 libX11-xcb.so.1 libX11.so.6 libXext.so.6 libxcb.so.1 libxkbcommon-x11.so.0 libXau.so.6 libXdmcp.so.6 libxcb-xkb.so.1 libbsd.so.0; do cp "$(find -name $i)" .. ; done
cd ..
umount x
rmdir x
Now we have extracted all the libs we need from raspbian, next step is to transfer them into steamlink's /lib folder (the hostname will be different for your setup)
Next we need to install the steamlink udev rules, but udev is readonly, so we just overlay it (run from rpi)
mkdir /storage/steamlink/overlay_work
mount -t overlay overlay -o lowerdir=/lib/udev/rules.d,upperdir=/storage/steamlink/udev/rules.d/,workdir=/storage/steamlink/overlay_work /lib/udev/rules.d
udevadm trigger
Now the steamlink.sh that comes with it is not geared for libreelec, so copy this one over it
Now the final step is to stop kodi and start steamlink (run on rpi)
and when your done just restart kodi or "reboot"
I am quite impressed how well this works, everything ran smooth as silk. gj Valve!