While you may be having difficulties, the instruction that ALT throws focus to the menu button in any Chromium-based browser I've ever touched that has one is beyond question. It doesn't cause the menu to open, it does nothing but throw focus to the menu button at the upper rightmost position on the browser controls. It even does that in the Chromium-based Edge browser.
Left arrowing after that will take you, control by control, through what's there, eventually including the omnibar (address box), which is where the traversal by left arrowing hits its end point.
Brian - Windows 10 Pro, 64-Bit, Version 1809, Build 17763
Puritanism: The haunting fear that someone, somewhere, may be happy.
~ H.L. Mencken