I’m hard of hearing with significant loss in one ear, and almost total deafness in the other. I have had some experience of deaf people.
Hard of hearing people would not need sign language generally, but might benefit from other methods - loops; headphones; maybe bluetooth with the new generation hearing aids (limited range however); power point presentations of songs, responses and creeds and so on.
The profoundly deaf could benefit from the power point presentations at least.
Sign language is a difficult skill to learn, and like any other language needs constant practice and repitition to maintain it. So interpreters are not easy to find.
But if it becomes obvious that there is a regular deaf attendee in the congregation, then one hopes that somebody else in the church family might make it their ministry to learn sign language, in order to make that person feel welcome and understand what is going on.
Deafness is a socially excluding disability, and to ignore the communication needs of a deaf person strikes right at the very thing they find most difficult - exclusion. That’s why they tend to stick together - the only people they can really relate to are those who speak their own language.
Generally speaking if you want to have a ministry with disabled people you need to either be as disabled as they are, or completely whole so that you can act as a conduit between them and the general community. On that basis, hard of hearing people are not best suited to ministering to profoundly deaf people, since we’re neither one nor the other.