ch341 is a common choice, but you may need to modify it for 3.3v operation, see Xiaomi Mi Router 4A Gigabit Edition (R4AG/R4A Gigabit) -- fully supported and flashable with OpenWRTInvasion
ch341 is a common choice, but you may need to modify it for 3.3v operation, see Xiaomi Mi Router 4A Gigabit Edition (R4AG/R4A Gigabit) -- fully supported and flashable with OpenWRTInvasion