I was searching for a cheap bridge to connect a printer to my Unifi network. I came across a few posts with this specific question (e.g: https://community.tp-link.com/en/home/forum/topic/101566)  but no firm answer so...

I can confirm that the RE200 can be setup in bridge mode! There isn't specifically a "bridge" option in the setup, you have to manually configure it which is simple.

There are two modes "Range Extender" and "Access Point", you want to choose "Range Extended". If during the setup it asked to create a new wireless network (to extend the range) just put whatever it. Run through the setup to connect it to your main network and afterwards go back to the "Wireless" settings. From there you can keep your "host" network active and simply disable the "Extended network". The Ethernet port will stay up and voila, bridge mode.

Hoping this will save others some time when doing research in the future.

Edit: Don't forget to turn OFF "DHCP Server" in the "Network" settings, it's on Auto by default.