I have been using Linux / GNOME as my primary environment for the last 20 years, but at my current job, that was not an option, so I'm on macOS.

I tried for a week to get used to the unfamiliar key bindings for text input, but then I gave up—I'm a vim user after all!—and found a system setting to use the bindings I am more familiar with. This was picked up by many applications, but notably _not_ by the Microsoft suite, which appears to have the default macOS bindings hard coded...

To me Ctrl+A was always "Select All", and it worked reliably on every system I had (except once when at my office I had a computer with unix bindings and the administrator told me he can't change them so I only used my laptop).

It’s an OS level thing (well, OS + standard widget library). As long as the app is using a native macOS text field, the OS has (and has since I think the first versions of osx) support for basic emacs movement keys, no extra effort on the app developers part.