Ubiquiti does not release change logs for the sake of vanity. Every update to the U6-LR addresses specific pain points. Here is what the latest firmware (e.g., 6.6.77 and beyond) typically includes:
Fix: Go to Device settings → RF Environment → Re-scan and auto-optimize channels. Often, new firmware resets channel selection. u6lr latest firmware
For advanced users managing devices without a controller: Ubiquiti does not release change logs for the sake of vanity