If you never had problems with Android and 5 GHz WiFi, then your problem is different from mine.
The reason for the installation of CoreELEC in the internal memory is because I do not need an Android whose WiFi does not work.
The reason for installing an Android firmware from a different manufacturer is because none of the H96 Pro+ firmwares worked well in CoreELEC for shutdown, suspension and CEC control. I was looking for a bootloader that would work fine because the rest (DTB, WiFi and bluetooth drivers, ethernet, remote control except for the IR signals on and off, …) is installed by CoreELEC or allows you to configure a remote control.
If you want to do something similar to what I did, you will need an IMG firmware and a male USB to USB male cable to install it, the ideal is the firmware of your X96 Mini (you should always have one on hand to recover the native operation of your device ), but you can also try firmwares from other reliable manufacturers that use the S905W processor (Beelink W95, Tanix TX3 Mini, etc.) because if you are going to install CoreELEC internally you only need the bootloader.
The sites I use to search for firmwares are the websites of the manufacturers, xda-developers.com, 4pda.ru, etc.