How to implement a domain that is not joined nor has trusts to the main domain

Hello,

i have a question about this use case:

i have to implement SPP+SPS in this environment with multiple domains. There's one domain that doesn't have trust to any domain (included the one where the appliances are) but it needs to be implemented in the PAM architecture.

How can i do so? Is it possible to implement it without trusts and being it only reachable by the appliance via network routes?

Thank you,

Simone