By default all switches layer 2 ports are in dynamic desirable mode so if you do not manually configure it as "switchport mode access" then it will try to from a trunk with remote port which generating DTP frames.
It is always recommended that if you do not want the port to form a trunk manually configure it as an access port.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...