Not sure about opera, but IIRC firefox doesn't use xdg-settings to set itself as the default browser.
chromium-browser relies on xdg-settings, which errors out when $BROWSER is set, and that's apparently intentional. So the bug here seems to be that $BROWSER is set in the first place. What purpose does that variable fulfill? As pointed out by Walter, it's not part of the UNIX standard.
Not sure about opera, but IIRC firefox doesn't use xdg-settings to set itself as the default browser.
chromium-browser relies on xdg-settings, which errors out when $BROWSER is set, and that's apparently intentional. So the bug here seems to be that $BROWSER is set in the first place. What purpose does that variable fulfill? As pointed out by Walter, it's not part of the UNIX standard.