I had a Psion series 5mx and it was amazing. The keyboard was not quite big enough for me to touch type, but it was fast enough to take notes. The apps were extremely well made despite greyscale screen. Where I was, the most popular competitor were Palm devices. The larger screen and integrated keyboard made me feel like a king compared to those around me using Palm devices. I was sad to hear that Psion was pivoting to phone operating systems with Symbian and did not get a chance to try any of their other devices or form factors (Psion series 7, netPad, etc.)
Later I had a Blackberry Curve. It had the best keyboard and form factor for mobile typing I have ever used. The keys were smaller than the virtual ones on onscreen smartphone keyboards, but even today I prefer the physical buttons and cannot type as fast or as accurately as I could on the Curve.
Today I use an Android smartphone with Termux (https://termux.dev/en/) and occasionally bring along an external bluetooth keyboard if I plan to use it for more serious work. If there were a mainstream brand Android smartphone with an integrated physical keyboard, I would buy one immediately. There are a few off-brand smartphones with physical keyboards, but they are not well-maintained (typically running older versions of Android with few or no security updates) and some have questionable build quality and heritage (e.g. might come with factory-installed malware).