Yes. For UniFi, in the properties of the switch, go to Ports and click on the edit button for the port that should become the mirror. Then click "+" next to Profile Overrides. Under Operation, select Mirroring. Type the port number that should be mirrored and Save. I did this with a UniFi Switch 8 POE-150W.

Probably so, the Security Onion wiki has some recommendations for affordable taps:

https://github.com/Security-Onion-Solutions/security-onion/w...