If you install libreELEC it means you also install kodi on your device. So, why you want to install kodi apk? Did you want to upgrade to the latest version?
Yes it is possible but complicated, why? you have to do so many steps (maybe using Android emulator, etc) and maybe it wouldn't work. Just install the latest LibreELEC on your device to get Kodi works great on the device, so simple.
So, you don't need to do many steps to install the Android app on libreELEC.