Unlike GPON (Gigabit Passive Optical Network), EPON requires specific timing and authentication protocols. This is why generic firmware usually fails on these units.
However, like many carrier-grade devices, its out-of-the-box potential is often locked down by the Internet Service Provider (ISP). This is where the concept of comes into play.
Often requires specific login credentials or bootloader access Common Firmware Custom "Blue" Firmware Common Firmware V9.0.11P1N15 (and similar) Important Security & Compatibility Notes