alt Hacker Newson Windows I can press Alt and see a letter underlined in the menu to let me know what keyboard shortcut activates it
Have you not noticed that every MacOS menu item that has a keyboard shortcut has the entire shortcut listed on the right side of the menu? This goes back all the way to System 1 in 1984: https://web.archive.org/web/20140512112637/http://www3.nd.ed...
It's somewhat more obvious when you're using a keyboard that actually has all the same symbols on the meta keys; Apple likes to drop those sometimes and it's really not helpful for someone who hasn't learnt the cryptic glyphs. The ancient Magic Keyboard on my desk only sports a ⌘ on the Command key, and lacks ⇧ on the shifts, ^ on control, and ⌥ on the alts.
You can even navigate the menus entirely by keyboard, if you turn on "Full Keyboard Access" in the Accessibility prefs. https://support.apple.com/guide/mac-help/navigate-your-mac-u...
but if I want to "show package contents" of an app in the Applications, I definitely need a mouse!
With Full Keyboard Access on you can hit tab-m to bring up an app's right-click menu and navigate to it. FKA has a lot of tab-something shortcuts.
Menu items on Windows can have 2 shortcuts - a keyboard shortcut like the macOS equivalent, that can activate the item when the menu is closed, and an access key, that can be used to activate it when the menu has keyboard focus. See https://learn.microsoft.com/en-us/previous-versions/windows/...
(The access key concept applies to many other types of control. Anything with a text label can have one, pretty much.)
The shortcut is indicated towards at the side of the menu bar, like macOS. The access key is indicated by an underlined letter. For example, in Firefox, the File > Save Page As... menu item has a shortcut key (Ctrl+S), and an access key (A). The A in As is underlined to indicate the access key, and there's a right-aligned Ctrl+S in that row of the menu bar to indicate the shortcut.