I had a foldable one with (almost?) full-sized keys that I really enjoyed using. It connected via infrared, which was a bit strange but made it compatible with different generations of device connectors.
"I have fond memories of some z-machine interpreter on the Palm that I found easier to play with than anything on my desktop computer. There were lots of shortcut buttons and thanks to the stylus it was still easy to use those (vs a touchscreen using ony fingers where you need huge buttons to hit). You could also tap any word in the output to bring up a context menu of actions (e.g. to examine or pick up objects mentioned in room descriptions) and that list of actions was a combination of a configurable global list and a game-specific list you could add actions to. Could play through entire games and barely ever have to type anything. Had a folding keyboard, but no memory of using that for interactive fiction."
From looking at my old hoarded palm files I think that the interpreter was PalmPilotFrotz, still available on the if-archive: https://ifarchive.org/indexes/if-archive/infocom/interpreter...
On smartphones, FDroid for Android had the Anysoft keyboard with a swipe option, it works great, much better than typing. There's also some grafitti 'keyboard' input at FDroid, but I prefer the swiping one as it's far superior.
On the old T9 phones, OFC a Frotz port exists for J2ME, but I didn't try it.