I used to have a solution working where I ran an Access point in “AP client mode” and I could then throw a switch behind the access point and it would bridge all the clients behind it over wifi to my main router/ap.

Does the 2111 set on the Data WLAN support bridging multiple devices or does it just support 1 device behind it?

2111 acts like a wireless bridge and connects to the WiFi network like a client. Note that this unit does not have AP mode.
Yes you can have multiple wired clients behind the 2111.

Also note that 2111 uses WDS mode which means the target AP should also have such support.

ok, so if I take the 2825 (which I currently have) and a 2111 it should work since they are designed to work in this mode. I don’t need it to also act as an access point, I just need it to support bridging multiple devices behind the 2111. Which it sounds like this should work.

But it seems like the 2211 apparently doesn’t support this WDS mode bridging since I tried this unit already and only 1 unit can connect behind the bridge.

You are correct about the 2211-DZ. The latest 2211-NG lets you connect multiple clients behind it when operating in bridge mode.