Any device (video endpoint or mobile user) you have on the Pexip service, residing under the same company as the Google Interop service, will be trusted. (If you are on the Pexip service, all your devices will most likely be in the same company as the Google Interop service. If in doubt, please ask your Pexip partner.)
This is independent of whether you use your own domain or the shared domain (gmeet.pexip.me).
Skype for Business clients are not on the service and hence not trusted.