Some quick googling suggests the mirror ports sounds like a good idea, but that it only mirrors it over the single switch rather than across multiple switches.
https://community.ui.com/quest…99-4fad-b08b-7ed06d29fcdb
https://community.ui.com/quest…4e-4857-81dc-ed5f999799c0
https://community.ui.com/quest…ea-42fd-91f0-d6136e9c2afc
I'm guessing by this thread your dvr doesn't support the ability to tell it what ips your cameras are on? Because ideally you'd run the dvr and cameras in a separate vlan and just have the dvr look for the devices then on the network.
I'm not sure I have a better suggestion off the top of my head, I've seen similar things to this done before but I think what you're trying to do might be subtly different if the dvr needs a "direct" connection to the cameras.
Only other thing I'd try potentially is running each of the cameras on its own vlan which is then broken out on the switch going to the dvr, but I'm not convinced that'd work either.