So... the OrangePi i96 console doesn't run at the same speed, nor use the LS-UART1 pins, that most of the CE boards do. Instead it runs the UART at the same speed as the boot ROM and pins it out using normal 0.1" header pins.
This has some benefits (in particular it leaves the LS connector free to add sensors, etc) but can be a bit of a pain if the only 1.8v serial adapter you have is a UART serial mezzanine. Happily the two devices can work together:
Basically we take TX and RX pins from the i96 and hook them up to the centre pins of the UART0/UART1 selector header.
In the photo above I've got the UART adapter connected to the LS header. This is mostly for mechanical stability but it also ensures both sides share a common ground (and the reset button on the UART adapter is useful when developing).
It is possible to use the UART adapter whilst it is disconnected from the i96 but in that case we need either to ensure the i96 and UART share a common ground. Happily, if both i96 and UART adapter are powered by the same laptop then the ground is likely to be common already...