Create a Raw/Plaintext input instead of a Syslog input in Graylog and use extractors or pipeline rules to extract the information you need from the log messages.
Your reply spots on! I just need to create a raw/plaintext udp input and do not need to configure anything else. It logs all the info I need and source IP is the device IP.
Perhaps you could add this into your FAQ for user with Huawei devices.