The OnePlus Community forum (community.oneplus.com) is exactly what it claims to be: an official forum run by OnePlus for its users. That immediately answers the question of whether it's fake or a scam — it isn't. The site has been online for over four years, passes all major threat checks, and discloses the company behind it through a legal entity page. For a forum, the privacy policy and terms of service are more than adequate.
What about safety? The site uses a valid SSL certificate and hosted on Amazon Web Services, so your connection is encrypted and the infrastructure is solid. The main technical drawbacks are that it still accepts older, less secure TLS versions and doesn't set some browser protections that block common web attacks. If you're just browsing or posting, these aren't likely to cause problems, but they mean the security isn't best-in-class.
If you're wondering whether community.oneplus.com is safe for logging in with your OnePlus account, the answer is yes — but you should be aware that the site relies on JavaScript to load content, which makes some of its contact info less visible. Overall, this is a genuine community site from a trusted brand with some room for technical improvement.