You now don't need this driver for the MiSTer FPGA! It has been included inside the Linux Kernel since 5.14.

Thanks to Alexey for this!

Installation

• Download the .ko file in the Releases folder : LINK
• Connect to the MiSTer via SSH/FTP using either Serial Console or Ethernet or simply plug the SD Card in your computer.
• Transfer the .ko file to /lib/modules/(YOUR KERNEL VERSION)/
• Use a keyboard and press F9 or connect to SSH and type :

depmod -a
modprobe 8188eu
reboot

Compilation (Step by step)

On Debian / Ubuntu, I used WSL Ubuntu on my end :

• Install ARM cross-compile toolchain & build essentials : apt-get install gcc-arm-linux-gnueabihf build-essential
• Install Bison : apt-get install bison
• Install Flex : apt-get install flex
• Install OpenSSL-dev apt-get install libssl-dev
• Create a folder called build by typing mkdir build
• Go to the folder : cd build
• Clone the Linux MiSTer Kernel : git clone https://github.com/MiSTer-devel/Linux-Kernel_MiSTer
• Clone this repo : git clone https://github.com/icelaglace/MiSTer_WiFi_EW-7811UNv2
• Delete .git folder inside the Linux-Kernel_MiSTer & MiSTer_WiFi_EW-7811UNv2 folders (Recommended by Sigurd Bøe)
• Go to the Linux MiSTer Kernel folder and type :

make ARCH=arm mrproper && make ARCH=arm MiSTer_defconfig && make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- EXTRAVERSION=-MiSTer modules_prepare

• Once it's done, go to MiSTer_WiFi_EW-7811UNv2 folder and type :

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- clean && make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- KSRC=../Linux-Kernel_MiSTer modules

KSRC is the path of the Linux kernel you just compiled, change accordingly if you didn't follow the exact instructions

Compilation (copy and paste) for Debian-based distributions

apt-get install gcc-arm-linux-gnueabihf build-essential
apt-get install bison
apt-get install flex
apt-get install libssl-dev
mkdir build && cd build
git clone https://github.com/MiSTer-devel/Linux-Kernel_MiSTer
git clone https://github.com/icelaglace/MiSTer_WiFi_EW-7811UNv2
cd Linux-Kernel_MiSTer
rm -rf .git
make ARCH=arm mrproper && make ARCH=arm MiSTer_defconfig && make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- EXTRAVERSION=-MiSTer modules_prepare
cd ../MiSTer_WiFi_EW-7811UNv2
rm -rf .git
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- clean && make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- KSRC=../Linux-Kernel_MiSTer modules

Troubleshoot

• If you don't have the .bin /lib/firmware/rtlwifi called rtl8188eufw.bin,go to https://github.com/wkennington/linux-firmware and download : rtlwifi/rtl8188eufw.bin
• Transfer the .bin file to /lib/firmware/rtlwifi

Thanks to this guide for the instructions :)