The Commodore Callback 8020 smart flip phone

https://josebriones.org/dumbphone-finder>

Once you're into the Android or Android-adjacent OS territory (LineageOS, SailfishOS (the Callback runs this), /e/OS, iodeOS, etc.), prices approach flagship mainstream Android or iOS devices ($600+ generally), and GrapheneOS specifically requires Google Pixel, at least until the Motorola partnership bears fruit.

And yes, scale of production and the need to be self-supporting rather than relying on business partnerships, advertising, and surveillance capitalism does tend to incur some price premium, though it's still quite possible to find affordable options.

I'd strongly recommend taking a look at Jose Briones's Dumbphone Finder (mentioned and linked above), his website (https://josebriones.org/>), Substack (https://josebriones.substack.com/>), and YouTube phone-review channel (https://inv.nadeko.net/channel/UCFtVwG0NFd6gT3TXfMCU7oA>) in general, and /r/dumbphones on Reddit for more information. I'm going to write a longer top-level comment summarising the current state of my own research into this topic.

There is a larger community oriented around alternative mobile devices including more reviews and technical information. Given that manufacturers often obscure rather than clarify features and capabilities, this is often a preferred source.

Edit: Corrected device support, originally mis-stated LineageOS as restricted, rather than GrapheneOS.

Don't let the form factor fool you, this is not a dumb phone.

https://www.dumbphones.org/>

The other way to go is with an ultra-small laptop (typically 12--13"), a tablet with integrated keyboard, or a (usually DIY) cyberdeck.

I used a TP-Link M7650 when I was cut off from fiber for a while and it worked great for me.

My wife hates every smartphone that is currently in the market. They are all too huge for her. She has an iphone SE which was the best compromise at the time, although she still finds it big. She doesn't want to get a new one, because there is nothing on the market of that size. She doesn't use most the smart features. She only uses it for chat with family and friends and getting email notifications (and reading them, but never replying on the phone). She also uses it as a camera. And calls, including video calls. This might be a solution, although for some reason they say "no email app". I'm hoping you can add one later.

And then as a child's phone to keep them off social media, while also having a chat app to actually communicate with them.

Even for me, it's been some years too that I've been thinking that I don't really need a smartphone. I mostly need a device that I can use to make calls and that I can use as a hotspot for connecting other devices such as a laptop when I need to.

The keyboard will definitely not be an issue. I'm old enough to remember teens using those kind of keyboards typing blindly in astonishing speeds, even without T9.

Lack of 5G might be an issue.

The price is steep. I'm not sure if that is going to be a problem.