I have a V31R version of X96 Max, so the firmware, recommended here, does not suit me (update won’t start from recovery).
So I’ve taken Android 8 firmware for V31R, exactly: x96Max_V31R_20190716-2201 . Which can be downloaded here: https://mega.nz/#!OxJCCYaC!lIHKY9lcsWwM9jUA14o9rV0cwbpyaUkfXqVgGfLNSjA
After update I get gigabit network working just fine.