For a traditional style remote, held in a pointing grasp with thumb on top, I have a hard time imagining something much better than a T9 layout.

Personally, I'm kind of enamored with the idea of a phone or tablet for media selection & control.

On touchscreen based devices, I'm a big fan of https://en.wikipedia.org/wiki/MessagEase.

When I started looking into alternative text entry for a phone, the big thing I was looking for was the ability to completely disable predictive text entry. Messagease allows for that - I'm able to input text quickly, accurately, and without the use of predictive input.

I've used it while holding my phone in either hand and using the thumb of that same hand (though it works better in my dominant hand). I've also used while holding the phone in my non-dominant hand and using the index finger of my dominant hand.

I can almost, but not quite, use it without looking.

So, if you're thinking of a custom remote project to scratch that itch, that layout may provide inspiration.

Looks like it’s patented? That might inhibit use a lot.

Perhaps https://twiddler.tekgear.com/ ?