YouYeeeToo X1 UART levels

I have a simple question. I see that the UARTs have a 3.3v associated with them.
Are the RX &TX only 3.3v or are the 5V compliant also?
Would like to use the UARTs for testing using (PuTTy) on Embedded hardware, some 3.3v and some 5v, but don’t want to burn up the RX if it is only 3.3V and can not handle a 5V level.

Thank you
Michael

1.8V or 3.3V

Thanks for the pinout and schematic.
if I’m reading this right … the TVS diodes on each input are ST0541D4 which have a clamp voltage of 11 and a breakdown voltage of 5.5vdc to 9vdc …
Since it appears it is above 5Vdc it should accept standard TTL logic of 0-5Vdc for the inputs

Thank you.
Michael