Thanks for reporting this.
The Snort3 standard is to use lower case letters to spell configuration parameters.
The parameter should have been named host_tracker.ip instead of host_tracker.IP. We will make that change.
Hello, found that in snort-3.0 beta 247 bug in host_tracker:
bool HostTrackerModule::set(const char*, Value& v, SnortConfig* sc)
if ( host and v.is
("ip") // must be "IP" (as defined in HostTrackerModule::host_tracker_params)