Some trauma T's can be trained to provide IFS, depending. My T has worked with DID in the past, and she was connected with the vet center, so I lucked out in being referred to her from the local VA Hospital. Where I used to live, there were no VA providers to help me with DID. My veteran friend who moved out of state as well found a DID therapist in a different state, but then had to move and then transferred to a T who is willing to learn to work with IFS and other options. It's possible trauma-informed therapists and trauma specialists can learn IFS to help out DID clients.

IFS is basically learning to communicate with different parts of self. It takes time. It takes patience. It takes having a really good rapport with your T to feel safe enough to open up that way. IFS is used for both DID and for those with Complex PTSD and dissociation. For those with DID, it helps us to be more co-conscious and less dissociative over time. For both DID and PTSD, IFS helps to bring past traumas to awareness by being able to learn more about our dissociated selves.

For DID, we have multiple parts of dissociated selves (at least two distinct selves).
For Complex PTSD with dissociation, they have dissociated the traumas, they may have an internal child part that holds childhood trauma memories and feelings, etc.
There's other variations to this, based on people with other dissociative disorders or comorbid PTSD with a dissociative disorder.

My T transitioned from the VA system into private practice. I still see her. We still use IFS to help me when I'm feeling "floaty" and dissociative, when I'm struggling with very strong emotions, when I'm scared, when I'm triggered, etc. Sometimes I feel something, and then I dissociate. I realize that there's another part who is really affected by a trigger, and who helps me and my system by being protective of that.

It's hard with DID because our systems are designed to dissociate automatically, to protect ourselves and our thoughts, and to be hidden from anyone knowing what we know and feel. So, essentially, IFS unpacks all that - only, we can still be ourselves and be safe. It takes a while to get in the place of being ourselves and being safe while coming out. It takes many baby steps.