The legacy device tracker DeviceScanner was replaced with the new device tracker implementation ScannerEntity.
You should remove references to platform asuswrt in device_tracker section in your YAML configuration and update person device tracker with the new entity.
The YAML key dnsmasq, interface and require_ip now are managed as integration options. The values present in YAML are imported in the options the first time that the integration is loaded.
All sensors are initially created as disabled and can be enabled from ASUSWRT device configuration instead of using YAML configuration.