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According to the instructions, it should be possible with the following steps:

Please follow the steps below to put the Ubiquiti UniFi U6+ access point into bridge mode:

1. first, install the UniFi Controller on your computer or server and add your Ubiquiti U6+ APs.

Open the UniFi Controller and navigate to the UniFi U6+ Access Point you want to put in Bridge Mode.

Click the Configure icon and select the Network Settings tab.

4. go to "Network Type" and select "Bridge".

5. deactivate the option "Separate network" and click on "Apply".

6. restart the access point to apply the changes.

Your Ubiquiti UniFi U6+ access point should now be in bridge mode, acting as a Wi-Fi only access point that does not change the network it is accessing.