Honestly, the ability to override menu keys is really a long-running flaw in browser UI, IMHO.

Firefox acquired a not-so-obvious way to disable that for a given site:

Click the "lock icon" to the left of the URL in the URL bar. Click "connection secure". Click "more information". In the window that comes up, click the "permissions" tab. On that page, there's an option to "override keyboard shortcuts". You can click "Block", and it'll prevent that particular website from overriding your keybindings.

This had been a long-running pet peeve until I ran into someone explaining how to disable it. I still bet that a ton of people who can't find the option put up with that. Like, lemmy Web UI keyboard shortcuts clash with GTK emacs-lite keybindings, drives me nuts. Hitting "Control-E" to go to the end of the line instead inserts some Markdown stuff by default.