No, Atlassian Cloud sites all live at <something>.atlassian.net
Atlassian recently announced that this is not going to change in the near future. They have "allow other domains" story open and they were working on it, but they've said it's not going to happen in the next few years.
Hi All! We’re excited to share the launch of an announcement banner that lets Jira site administrators communicate directly to their users across their Jira Cloud instance. ...
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