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The Answer Bank - The Answer Bank is the UK’s leading question-and-answer site.
Blurtit - Blurtit is a Q&A website. You can ask a question or answer on any question.
Question2Answer - A Q&A site helps an online community to share knowledge.
AllAnswered - Your Team's Collective Brain All-In-One Knowledge Management System Wiki + Q&A + Workflow + AI
Scoold - An open-source, enterprise-friendly Q&A platform inspired by Stack Overflow.