What keyboard shortcuts are you missing in Linux? At least with KDE, I can go the entire day without touching the rodent. And on the rare occasions that I do use the mouse, I'm mostly touching it only for webpages that don't work with Tridactyl, or for highlight-middle-click copy-paste.
I miss the ability to set arbitrary shortcuts and bind them to arbitrary menu items. Also, shortcuts are not very consistent across Linux applications, compared to macOS, which is much more homogenous and less surprising. OTOH, that's not a deal breaker and I keep using both Linux and macOS daily.
macOS is frustrating to use without a mouse. On one side the shortcuts are consistent, work everywhere, and are very deeply customisable. Really much better than anything I have tried on other platforms. All the menus are very easy to use without a mouse once you know the shortcuts (which, granted, are not obvious if you don't know they exist). Emacs-like shortcuts in all text fields are absolutely fantastic. The fact that Command is used throughout the GUI leaves Control available for things like terminals, which is awesome (e.g. there is no conflict between Control-C to kill a process and Command-C to copy some text). But at the same time there are things like window management that pretty much require a mouse, but really should not.
> I miss the ability to set arbitrary shortcuts and bind them to arbitrary menu items.
In each application? Interesting that the OS provides that.
> macOS is frustrating to use without a mouse.
My experience confirms this as well. I was really expecting an ergonomic, well-polished experience but I found that the Mac is polished like shark skin. It's nice and smooth if you do things - or can force yourself to do things - like the engineer in California does things. But if you like to keep your hands on the keyboard, or organize your applications (not just windows but applications), or anything else then you are going against the grain and that smoothness turns into obstacles and pain points.
