The closest word I can think of is a sycophant but that’s too strong word and not exactly what I’m looking for. The word I’m thinking of has negative connotations and it’s for someone who is friends with different groups but only at a superficial level and isn’t necessarily honest about who all they’re friends with. This person would be seen as untrustworthy.
What about perfidious gadabout?
I think your focus is on the disloyalty, but really there are two aspects of your description that make it difficult to find s single word which fits well. I’m also thinking the individual isn’t necessarily disloyal, but rather loyal to an unseen cause. E.g., disingenuous. If the person is a plant, then “mole” comes to mind.