Look at the response headers for Onion-Location.

If your browser (e.g. Tor Browser or Brave) offers a button to open the .onion site directly, you will be taken to one of these pages:

• Brave if your browser split the first Onion-Location on commas.
• 404 page on brave.com if your browser merged all Onion-Location headers and used the resulting string verbatim.
• A different 404 page on brave.com if your browser only used the first Onion-Location header verbatim.
• DuckDuckGo if your browser followed the second copy of the Onion-Location header.