After some month, my experience with Android TV is now complete. These are all the stuff that I configured/bought:

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• https://www.amazon.es/gp/product/B07V5K6LSF/ very convenient adapter with gigabit port (that I actually use) and some other USBs, 100% supported. I suggest AX88179 adapters for ethernet, they works just fine.
• A USB stick that I use as external storage mainly for game ROMs (cause the compatibility with retroarch is pretty good)
• prim-ftpd as SFTP and FTP server (useful for transferring files from PC) https://github.com/wolpi/prim-ftpd
• TV Bro as main web browser (the best in my opinion) https://github.com/truefedex/tv-bro

TIPS:

If you are having problems with the USB port, disable debug USB if you have enable it because it disables all the (other) function of the USB port as storage, networking etc...

little OT:

for PSX emulation I suggest to use PCSX ReARMed as core, other cores with this Mi Box gave me errors, PCSX ReARMed just works!