The RTL8188EU is not well supported. Use the urtwn driver, but expect instability. For a firewall like pfSense, buy an Intel card instead.
Do not expect miracles. The Realtek RTL8188EU is a single-stream, 2.4 GHz only chipset. The RTL8188EU is not well supported
Pro tip: For 5 GHz or speeds above 100 Mbps, upgrade to a Realtek RTL8812AU or RTL8821CU chipset. The RTL8188EU is for light browsing and IoT projects. Do not expect miracles
sudo apt install raspberrypi-kernel-headers
git clone https://github.com/aircrack-ng/rtl8188eus
cd rtl8188eus
sudo make && sudo make install