I sometimes wonder if modal editing (like vim uses) might be a good approach for navigating/editing longform text on touch devices. It does seem like a missed opportunity to have taken the keyboard/mouse approach and then transferred it to touch devices. Even the keyboard layout has no real advantage for two thumb typing on a screen. Approaches that adapt the interface whilst leaning heavily on letter based inference…
In gboard we've already got modal stuff for numerical keypad, emojis, special characters (2 different modal pages), etc. Adding one more modal keyboard page for cursor-editing (arrow keys, ctrl-arrow-keys, home/end, pgup/godown, select-toggle-button, delete, rclick menu) would just make sense. Would just be getting the rest of the desktop keyboard into the phone keyboard, nothing groundbreaking.
[0] https://www.xda-developers.com/gboard-v6-2-adds-cursor-contr... (2017)