Windows 11 has stricter driver signing requirements and a new network stack. The default inbox driver (Microsoft’s Generic NDIS driver) does not unlock the full hardware capabilities of the RTL8812BU. It forces the card into a "compatibility mode" that caps speeds at 150 Mbps and frequently drops the connection during heavy load.

listed for Windows 10, which generally remains the most stable base for Windows 11. Device Manufacturer

: Supports up to 867 Mbps on 5GHz and 400 Mbps on 2.4GHz using the 802.11ac Wave-2 standard.

Windows 11 aggressively manages power to USB ports, often cutting power to your Wi-Fi adapter, causing lag spikes.