How to fix 'Thunderbolt Bridge Not Connected' on MacBook Air?

Thunderbolt Bridge (a.k.a. internet Protocol over Thunderbolt) has nothing to do with letting you use your wired mouse or keyboard. It is a way of using Thunderbolt as a network interface, like an Ethernet interface or a Wi-Fi radio.

I am not in front of my Mac right now, but I suspect that if you turn on this mode, the port in.question will be unusable for attaching USB, USB4, DisplayPort, and Thunderbolt accessories. Why? Because yiu have told the computer to repurpose it as a network interface.

I would suggest ignoring any YouTube video that tells you to turn on this mode to connect a keyboard or mouse. If there are such videos, they are likely leading you down a rabbit hole.

Just looked at the setup on my Mac, which is running macOS 15.* (Sequoia).

It is normal for there to be a Thunderbolt Bridge service that is "Not connected" if Thunderbolt Bridge is not active on any Thunderbolt port. The presence of inactive Thunderbolt Bridge service, alone, does not interfere with other uses of the port. (If it did, my monitor and my external drive would not be working.)

Apple Support – Mac User Guide – Use IP over Thunderbolt to connect Mac computers