Hi,
There is no existing RT kernel package for Orin Nano developer kit with rootfs in NVMe SSD. Please refer to steps in developer guide to build the packages. You can set up the environment by following the steps:
No data from Joystick Logitech-f710 - #10 by DaneLLL
To ensure you have the environment which can build default kernel, flash it to Orin Nano developer kit, and the developer kit can boot up. And then you can try to enable RT kernel.