"add a keyboard" isn't an answer.
The best keyboard in the history of mobile computing was by Blackberry.
Blackberry (original and clone) physical keyboards are now available for both Android & iPhone, with some effort.
Sadly we never got a hardware successor for the dearly departed N900 Maemo and N9 Meego.
More importantly, it’s not realistic to think it will ever be as good as a real keyboard for lot of text entry. I expect dictation to do a better job for data entry.
In fact, this comment was created using dictation on an iPad, almost flawless, not much editing needed afterwards, and you can always use a keyboards if you prefer.
Demo - https://twitter.com/ashconnor/status/1776689029700075749/vid...
I have my own keyboard layout that I use since at least 2011, with drivers for macOS, windows, and Linux. I have no way to make it available on my iPad.
[1] https://qmk.fm/
[2] https://zmk.dev/
On iOS/iPadOS, touch-hold the virtual space bar and it becomes a trackpad for fine positioning of the cursor.
Magic Keyboard is a laptop-quality input device where capslock can be remapped to Esc for vim editing in ssh.