I haven’t tried this on Nano, but with R31.1 on Xavier, I have been able to run tigervnc-scraping-server and remotely connect from a TX2 R28.2 with xtightvncviewer (prefered, but most of other VNC viewers work as well).
The scraping server requires an open display to clone, so you would set your user (belonging to video group is mandatory) as auto-login (you can do that from Ubuntu settings), so that a display is created at startup before launching server.
If you have no monitor connected, the display may be 480p only.
If you have a monitor connected, it will be the size decided by nvidia xserver for your monitor from its EDID.
How to set a given resolution is still obscure to me…