The nightly images have the githash they were built from appended at the end of the name eg LibreELEC-RPi4.arm-9.80-nightly-20201020-dc19933.tar
Use that githash (eg dc19933 in the example) to look up changes on LE github.
You can also use the github compare function to see what has changed between two githashes. eg Comparing ec1292b...dc19933 · LibreELEC/LibreELEC.tv · GitHub
so long,
Hias