I am currently working in an environment implementing a Hybrid SharePoint deployment.
On-premise we have 3 environments in 2 AD domains.
Prod SharePoint - (Prod Domain)
Pre-Prod - (Prod Domain)
Development - Development Domain
Now the issue comes in the SharePoint online tenancy setup - Prod is talking to our Production tenancy and Dev talks to a separate tenancy because its in a separate AD domain.
The only tenancy we could link Pre-Prod to is our Production Online Tenant but we would need to do some form of data segregation to ensure prod users can only see prod data and pre-prod users could only see pre-prod data.
How do other people do this?
The only other option is to accept the risk we can't test hybrid functionality in Pre-Prod which isn't ideal.