macOS has a variety of apps like Homerow, Shortcat, and KindaVim (watch the videos in those links if u can) that allow for navigation of apps using just the keyboard. Homerow allows for pressing a hotkey and then showing letters over UI elements which can be entered to move the mouse to said element, similar to the Vim easymotion plugin. KindaVim attempts to implement vim modal navigation inside GUI apps, so you can enter normal or visual mode and use j and k to move up or down. They all work using macOS’ accessibility API which exposes UI elements for programmatic interaction.
I did a bunch of searches for Linux equivalent of such apps and Mac’s accessibility API, and didn’t find anything as comprehensive. Can you navigate a wide variety of Linux apps using mostly or only the keyboard (apps made with GTK, Electron, etc.)? Is it currently possible to develop an equivalent of the apps listed above?
I think you may be looking for a programmable keyboard.
With one, you can have arrow keys on the home row like vim, and make other universally recognized keys easy to reach including Home, End, PgUp, PgDn, App (right click), and all the modifiers. Some also build pointing devices into the keyboard as well.
I primarily use the Unicorne by Boardsource.