I was able to get my FQQ quad monitor working again after the macOS 26.5 (25F71) update on my 16-inch MacBook Pro M3 Max.
The issue appears to be related to the older DisplayLink/FQQ drivers not being fully compatible with macOS 26.5.
i have the FQQ 16 inch quad monitor .
16" Laptop Screen Extender Monitor Portable, Quad Monitor, Just 1 Cable for 3 Screens, FHD 1200P IPS Laptop Extender Compatible with Wins/Mac for 13.6" - 18.5" Laptops
What fixed it for me:
Completely uninstall the old DisplayLink/FQQ drivers
Reboot the Mac
Install the updated driver provided by FQQ:
https://www.ideaworldhk.com/xzzx
Re-enable Screen Recording permissions for DisplayLink Manager in:
System Settings → Privacy & Security → Screen Recording
Reboot again
After doing this, the monitors were detected properly and started functioning again.
Hopefully this helps anyone else experiencing the same issue after updating macOS.