After installing a fresh version of LibreELEC v8.90.004 Generic(LibreELEC-Generic.x86_64-8.90.004.img.gz) it seems that inputstream.adaptive isn't included with Kodi in this build.
Bash
LibreELEC:~ # find / -name "*inputstream*"
/storage/.kodi/addons/script.module.inputstreamhelper
/storage/.kodi/addons/script.module.inputstreamhelper/lib/inputstreamhelper.pyo
/storage/.kodi/addons/script.module.inputstreamhelper/lib/inputstreamhelper.py
/storage/.kodi/addons/packages/script.module.inputstreamhelper-0.3.3.zip
/usr/share/kodi/addons/kodi.binary.instance.inputstream
Without this I'm unable to watch both the Netflix and Amazon addons as it is a dependency for both.
Any help would be appreciated.