When my late wife was getting to the hospice stage one of the important messages they gave us was not to call 911 whenever she finally died. That would require the paramedics to come, attempt resuscitation, drag her to the ER, etc. All for naught.
Instead, once hospice was in place, we were to call them when she died. A doctor or nurse would come out, certify the death, then the funeral people would be called to pick up the now-officially dead body.
In the actual event, it eventually became clear she was dying imminently and we had a hospice nurse at home with us the last ~36 hours. When she finally did die, the nurse gave a report and vitals to an on-call doc, he said “yep, she’s dead”, and the body removal service (a subcontractor of the undertaker / funeral home) was called.
Different case:
My late aged MIL lived in an independent living facility. The sort of place where you have your own apartment and your own daily life but they check in on you every morning. She was old and raggedly but there was no particular reason to think she didn’t have a couple more years life left in her.
One night she died next to her bed. She was found that morning by the room-check person sitting on the floor. Presumably she’d gotten up to use the bathroom or whatever and had not quite made it to/from bed.
Their policy was they always call 911 as well as the family. Police and paramedics showed up and somehow she was declared dead. Paramedics left, and the police were still there awaiting the body removal people when I arrived.
Not sure what all that proves, but there’s two semi-recent experiences to choose from.
My advice:
If you have an elderly / frail person in your life, have a convo now with them and with their doctor about exactly this situation. Calling 911 is probably not the best thing, but in the absence of any prior planning it’s probably the only thing.
How exactly your local 911 service will react to your description of the decedent’s condition depends on their local procedures manual. Which might be not what you want or might be just the thing given the realities.