default or selected kernelversion does not have config value CONFIG_ECONET_AUNUDP.
Result is shown for kernelversion 6.2.5

AUN over UDP


Linux Kernel Configuration
└─>Networking support
└─>Networking options
└─>AUN over UDP
In linux kernel since version 2.6.12  
Say Y here if you want to send Econet/AUN traffic over a UDP
connection (UDP is a packet based protocol that runs on top of the
Internet protocol IP) using an ordinary Ethernet network card.