If you dive into therapy, I have noticed that a provider will list dissociation or dissociative disorder as a specialty. I feel it is important to feel the provider out to see if they see plurality as a disorder or as a healthy human experience or as something in between.
Here is some further insight from a therapist
Another resource called Internal Family Systems; https://ifs-institute.com/resources/articles/internal-family-systems-model-outline.
This is a peer created Dutch website that has some interesting videos and written resources; https://powertotheplurals.com/.
If you would like assistance in finding local resources, you can reach out to Galyn