What I’ve seen with my own eyes:
Non-bi-ritual priests, vested either in choir or in roman liturgical vestment, may concelebrate, or may sit in choir. In either case, they receive by coming to the altar table, and the celebrant hands them a piece of Body. They then take the cup by themselves, and drink of the Blood.
If they are not known to the celebrant, and do not have the requisite letters of introduction, I’ve seen the celebrant have them sit in choir… but communed them as above.
Visiting deacons, however, generally are communed as with the laity.
My dad, a Roman Deacon, only vests in 3 diocese… the one he’s canonically vested in (Anchorage), and his diocese of birth, Detroit, since the bishop there granted him faculties while visiting family, and Rome. When he comes to St. Nicholas, he receives as a layman would.
And the pastors HAVE been aware he’s a deacon.
As to EMHC’s: I’ve NEVER seen one in the Ruthenian church. I have seen a Deacon administer Holy Communion. I know that Ruthenian Particular law allows them, but restricts them. Then again, the few parishes I’ve been to didn’t need them. The few times St. Nicholas hits enough people to justify a second MHC, we usually have concelebrants enough.