Some keyboard layouts use the AltGr key (which is in place of right Alt) to type special characters and that doesn't work. Nothing at all happens when trying to type one of those special characters. In practice, AltGr is just both Ctrl and Alt at the same time. This is also kinda annoying, because just last week this exact same bug was fixed in another app after being present for over 2 months.

Almost all non-english keyboard layouts use AltGr afaik, so German, French, Croatian... As for examples, there's a Wikipedia page that lists them for many keyboard layouts. From what I know and have tested myself in the past, AltGr seems to directly map to Right Alt + Left Ctrl.

Do you have some examples to test this with? I.e. keyboard layout + combo + expected result.
Or even better, reference to what control sequences these should send?

One use case I ran into, when editing a (bash) file on an OC2 computer was with typing the # character.
Running Mac OS (Monterey 12.4) on a Mid 2015 15" MacBook Pro with a "British" keyboard layout (although likely not limmited to this specific hardware and software combination).
In order to type the # character, you must hold down the option key followed by the 3 key. On an OC2 computer, this resulted in a blank character (like a space) being input in the editor. Of course, my next step after that was to confirm that a # character could be input correctly by C&P, which was successful.

Interesting