Hearing aids that stream to a 'dumb phone'

We did that. He still has a hard time moving between the phone and text apps, and the dial screen and the one with audio, etc on it.

We did realize that he can’t text in a dumb phone.

This takes me back to trying to do all this stuff for my mother. I can really empathise.

A dumb phone simply isn’t going to work with those aids. You don’t mention the exact model but it’s only going to work with an iphone or- if the aids were made in the last few years- with an Android phone.

With my mother, I went down the route of installing various senior’s interfaces on her Android phone with varying degrees of success. In your father’s case, it’s a whole new interface which might destroy his remaining enthusiasm to engage with his phone.

You’ve tried this? Set up Assistive Access on iPhone – Apple Support (AU)10

As Morgan 1946 said, you can now hide all the apps (on the iPhone) that you don’t want to use. I know this is possible on the latest iPhone 16, I don’t know if this also applies to older iPhone models.
You could also put all the apps that he needs to use on the first screen, so that there is only one screen for him to look at.
I think the iPhone should suit quite well, but I don’t know my way around it sufficiently to recommend specifics - like voice to text

@Marie I dont know whether this is of any help

Samsung Galaxy A05s - Easology7

Samsung Galaxy A05s Easology - 6.7" 64GB

I just happened to see it as an advert in the paper and wondered whether it might be suitable.
Other than seeing it, I have no knowledge of how simple it would be to navigate
I do wonder if it is as simple as advertised