hello steamedcotton,
may I know which Jetpack release you’re working with?
env import should works if that’s not an old release version, please have a try to create an uEnv.txt under /boot .
or,
you may have a try to create boot.scr for the usage, please put it under /, otherwise it’ll load /boot/extlinux.conf.
for example, you should creating a boot.txt with the following contents.
setenv fdt_copy_node_paths
setenv fdt_copy_prop_paths
setenv fdt_copy_src_addr
setenv fdt_del_prop_paths
and, executing the following command to create boot.scr, i.e. $ mkimage -A arm -T script -O linux -d boot.txt boot.scr
you should see below messages if the boot script works
Found U-Boot script /boot.scr