This website [1] (actually, its codepen [2]) has a demo and even describes all the user-hostile reasons why developers might want to disable the right click menu.

There are some other accessibility tricks that Firefox advertises [3] like ignoring website font and color choices.

Firefox also has native support for overriding website CSS [5] but "modern" websites often come with impossible to understand DOM and CSS structures (if they even use CSS and not just forcefully insert style into the DOM directly because separation of concerns is for losers I guess).

Then there are websites like Github and some shitty forum software that insist on hijacking keyboard shortcuts like Ctrl+F and Ctrl+K. You can go into about:config and set permissions.default.shortcuts to 2 (Services.perms.DENY_ACTION) to block websites from overriding shortcut settings by default. You can go into the site settings and manually enable them again by going to page info (ctrl+i), then tabbing over to permissions, and changing the value for "override keyboard shortcuts" from "default" to "allow". Or, you could simply block the websites that offend you from that screen without changing the default.

[1]: https://www.codeinwp.com/snippets/disable-right-click-contex...

[2]: https://codepen.io/impressivewebs/embed/zYYxepW?height=265&t...

[3]: https://support.mozilla.org/en-US/kb/accessibility-features-...

[4]: https://superuser.com/questions/318912/how-can-i-override-th...