Same as another recent report on this, that's a generic backend error ("Something went wrong on our end"), not something wrong with the site name you picked, points to a temporary issue on Atlassian's side during site provisioning.
A few things to try:
1. Just retry, sometimes it's a transient hiccup and works on a second or third attempt
2. Try a different browser or incognito window, in case something local (extension, cached session) is interfering
3. If it keeps failing, use the "contact support" link in the error message and reference your Trace ID (7acdcb0260e3418bbcabd0b3baea4af7), that lets Atlassian look up exactly what failed on their backend, which the Community can't do
Since there's a specific trace ID attached, Support is really your fastest path if a retry doesn't work.
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