I've never seen a device that wasn't 115200,8,n,1 and I would advise against connecting the 3.3v/5v pins on the TTL device (asking for shorting issues and power isn't required). Yes it's possible that UART output is blocked in bootloaders, but that's normally only major-vendor streaming boxes (Amazon, etc.) and you're seeing stuff on-screen so that's unlikely. Not sure what to suggest as the only time I've seen something similar is when I'm connected to the wrong pins, e.g. JTAG not UART.
Tempting though large ones are, and the square one is normally GND .. Have you tried the 3x little round pads that are labelled?