Is user.fm a scam? That's a fair question, but the bigger issue is that right now, user.fm doesn't appear to be anything at all. When you visit the site, you're met with a 404 error — the page simply doesn't exist. So before you wonder whether user.fm is safe, you need to ask: is there actually a site here to use?
The domain itself isn't new — it was registered back in 2014 through a well-known registrar, Gandi. That fact alone is neutral. What matters more is what the domain owner has done with it over those 12 years. There are no snapshots of user.fm in the Wayback Machine, which means the site has either been offline most of the time or changed hands repeatedly. There are no user.fm reviews or user.fm fake reports online either, largely because there's nothing to review.
For a personal project or placeholder domain, this level of opacity is awkward but not dangerous. No one's asking you to buy something or hand over personal data here. But if you were hoping to find a functional service or business, you won't. The simplest takeaway: user.fm isn't a working site right now, and there's no evidence it was ever anything more.