Your SEP 14.3 RU1 (and above) Linux Agent does not apply definitions from LiveUpdate Administrator 2.x
SEP 14.3 RU1 and above
The new SEP Linux Agent (introduced in SEP 14.3 RU1) requires different content to be downloaded and distributed by your LiveUpdate Administrator server.
The new SEP Linux Agent (introduced in SEP 14.3 RU1) requires the following content to be downloaded and distributed by your LiveUpdate Administrator: Client - SymPlatform Definitions (Linux)
Additionally, if you're using SEP 14.3 RU3 Linux Agent, you need to disable the Total Cloud Protection setting in your AV policy. Please refer to this article for more details.