nebulabg.webex.com is a subdomain of Cisco's Webex platform, which is a widely used video conferencing service. Right now, the page shows a 404 error, meaning the specific meeting or resource you're trying to access doesn't exist. That doesn't make the site itself a scam, but it does mean the link you received might be outdated or mistyped.
For a legitimate Webex meeting, you'd normally be taken to a login or join page. Instead, this one returns a 'Page Cannot Be Found' message. The site does have valid security certificates and links to Cisco's privacy and terms, which is a good sign. If you were expecting a meeting from a company called Nebula BG, this could be a broken link on their end.
Is nebulabg.webex.com a scam? No evidence suggests that. It's a genuine Cisco domain. But since the intended content isn't loading, you'll want to double-check the meeting invite with the organizer. Our verdict is Mostly Safe, with the caveat that the link appears dead.