If you’ve flashed and the system is up and running, is the repo installed?
dpkg -l | grep '\-repo\-'
If the repo is installed, then you have access to those packages via apt-get. To see a list of interesting packages from another Jetson (which can be a guide to knowing what to install on the eMMC version):
dpkg -l | egrep -i '(cuda|nvidia|l4t)'