The Nova doesn’t have built-in SPI flash to store boot parameters, so you’ll have to have an eMMC or microSD present on the system just for the boot partition (those are the only two devices checked for a boot partition).
In Armbian, edit the /boot/armbianEnv.txt file, which should look something like this:
verbosity=1
bootlogo=true
overlay_prefix=rockchip-rk3588
fdtfile=rockchip/rk3588s-9tripod-linux.dtb
rootdev=UUID=6a4b469d-1a51-47c4-a673-1d10cc6c7871
rootfstype=ext4
usbstoragequirks=0x2537:0x1066:u,0x2537:0x1068:u
Change rootdev to the UUID of the external USB device, and usbstoragequirks to the Vendor ID and Hardware ID of the USB device.
The Vendor ID (Vendor) and Hardware ID (ProdID) can be found by entering usb-devices |more which will return a list similar to this:
T: Bus=06 Lev=02 Prnt=02 Port=01 Cnt=01 Dev#= 3 Spd=5000 MxCh= 0
D: Ver= 3.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 9 #Cfgs= 1
P: Vendor=090c ProdID=1000 Rev=11.00
S: Manufacturer=Samsung
S: Product=Flash Drive
S: SerialNumber=0374018070012088
C: #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=304mA
I: If#= 0 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=usb-storage
E: Ad=01(O) Atr=02(Bulk) MxPS=1024 Ivl=0ms
E: Ad=82(I) Atr=02(Bulk) MxPS=1024 Ivl=0ms
In the above example, the Samsung Flash Drive's Vendor ID is 090c and the Hardware ID is 1000.