Ive checked my BIOS to see if there is a way to invert the function keys and there isnt. Just a way to disable Fn lock altogether. I checked in Windows and Fn lock does not turn on without using the command (Fn+Esc). Something in linux has to be enabling it. When booting into Manjaro, I initially see line of text describing my disk. At this time Fn lock is off. It then flashes breifly, showing the same line. When it flashes, Fn lock gets enabled. Hopefully this is enough detail to figure out whats going on.
Asus Vivobook E410M Latest stable Manjaro XFCE