Unable to detect implicit web page language in Opera

Environment

• OS version: Ubuntu 20.04
• Browser version: Opera 74
• Extension version: Release 2020-2
• Last working version: N/A

Steps to reproduce

Trigger language filter list recommendation notification (see #9).

Observed behavior

• Notification is not shown.
• Detected language is null.

Expected behavior

• Notification is shown.
• Detected language is not null.

Further information

Unlike in other browsers, calling browser.tabs.detectLanguage() in Opera appears to always throw the exception Cannot determine language. This behavior can be observed across multiple domains and languages.