Keyboard shortcut for main menu?
I can't seem to find one. For me, the only way to bring up the main menu is to click the Vivaldi icon in the extreme upper left. This seems discordant with the idea of a keyboard driven browser. Worse, once I have the menu open, there is not a single keyboard shortcut set up for any item at all. What's with THAT? I'd be happy if I could see a way to establish a main menu keyboard shortcut, but there doesn't appear to be any way to do this. Am I missing something here?
I don't think you're missing anything. Even if the menu is enabled in settings, it's unusable with the keyboard.
Not anything to fret about — it's still work in progress, and no doubt will get fixed sooner rather than later.