I just saw in the documentation update that the C9300-M and MS390 switches cannot track clients connected to the high speed ports:
Note: The following ports don't support Client Tracking features on MS390/C9300-M.
1. Ports with supported max speeds 25G, 40G, 100G.
2. Link Aggregation ports
If a server, or 3rd party switch with clients, is connected to one of these ports, will the device(s) simply not be seen, or will the be reported as being on another port? Surely the devices connected to those ports must be in the switches mac address table, so I am not sure why they would not be reported??? Hopefully it is a limitation of the current container architecture and the native IOS-XE version will fix it!