With the new design, if I go to https://addons.mozilla.org/addon/addon-slug/ it redirects to https://addons.mozila.org/en-US/firefox/addon-slug/ which claims the add-on is “not available for your platform”. But the real problem seems to be that it is assuming that a URL that doesn’t specify the application is referring to a Firefox add-on and then not providing a way to download it, as it used to do.
Would the devs consider fixing this? Or is it recommended not to use such non-specific URLs anymore. Even so, at the very least, that misleading message needs to be fixed. It’s non-compatibility with Firefox, not with the user’s platform.