They used to be discoverable with mnemonics (underlined letters) but those have been dead nearly thirty years…

these still exist on windows though? you just hold alt

Only works for like 20% of the menus though. I remember alt shortcuts reliably being on every single menu in early Windows (95? ME? XP?)

They died when people stopped using native toolkits and started making everything an electron app.

Economics be damned, if you're going to make a native app, use the OS provided toolkits.

Hah, I was thinking 3.1…

Yeah I only used it a little bit so couldn't remember if it had the "hold alt to see shortcuts" thing

GTK (and QT I do believe) also support this on GNU/Linux.

I remember using TweakUI to enable "always show underline for shortcut key" because that genuinely felt like it should be a default for better usability.

I wouldn't say they're dead, just more hidden (e.g. GTK4 only shows them when you hold Alt). AFAIK most toolkits still support them, but app developers also have to actually define them.