PBS Spacetime recently had a video on this: https://youtu.be/8hvzF5oQe1g?si=e9Tw0XrMILbf4Ql6

The abstract does a poor job of explaining one of the primary motivations of this research: if Alcubierre drives can exist, and can be built, then it seems likely a sufficiently advanced alien species would have built them. We could therefore find them by detecting the drive failures associated with the hypothetical tech, something which is likely easier than actually building the drives ourselves.