I think you need to setup the asuswrt platform in configuration.yaml before creating a device_tracker using the asuswrt platform. That is the dependency mentioned in the error log.
From the component page, you should have this. notice it starts with 'asuswrt:", not “device_tracker:”
I have the same model and also used telnet… apparently adding port 23 gets it to connect but all devices appear away after few minutes and the sensors don’t work either… been trying to look into it but no luck and apparently I can’t enable ssh on this model
But it didn’t work. It looks like @bythelake is having the same problem on the thread @Bobby_Nobble posted above and he has the same router model as me. It appears installing Merlin on the router solves the issue. I may try that next.