The instructions here will tell how to run OP-TEE on ROCK Pi 4 / ROCK 4 boards.
There are several versions of the ROCK Pi 4 board, each with 1GB, 2GB or 4GB RAM options. OP-TEE has been tested and is known to work with a Rock Pi 4 Model B OP1 4GB. Other variants will likely work too.
The console can be accessed using a USB adapter connected to the board as described in the serial console documentation.
Just follow the ":ref:`get_and_build_the_solution`" as described in
:ref:`build`. To flash the board you will need a USB type A to type A cable.
The make flash step will tell you how to connect the cable and use the
buttons.