TYPO3 Core

Here is a kind of reference for possible URL schema: https://developer.vimeo.com/api/oembed/videos
The whole parser looks a bit wired and should maybe be refactored. E.g. by using an URL object to parse the data instead of doing the string parsing with RegExp.
Also, the tests should be checked and verified.

There's another issue in https://github.com/TYPO3/typo3/blob/ae00ad424a1b04ab30712d4558acab276396cb13/typo3/sysext/core/Classes/Resource/OnlineMedia/Helpers/VimeoHelper.php#L99

rawurlencode(sprintf('https://vimeo.com/%s', rawurlencode($mediaId)))

The media ID is double URL encoded. This causes the slash between video ID and video hash to be encoded as "%252F" rather than "%2F". (The added "%25" is the second-time-encoded percent sigil.)

Correct would be:

rawurlencode(sprintf('https://vimeo.com/%s', $mediaId))

Example with a fake 'unlisted' video URL:

Original URL:
https://vimeo.com/123456789/abcdef1234

Correct (succeeding) encoded URL to attach to "https://vimeo.com/api/oembed.json?width=2048&url=":
https%3A%2F%2Fvimeo.com%2F7123456789%2Fabcdef1234

Incorrect (failing) encoded URL which TYPO3 actually attaches instead (with "%252F" rather than "%2F"):
https%3A%2F%2Fvimeo.com%2F123456789%252Fabcdef1234

Proposed elegant solution for the vimeo renderer (replacing lines 136-147 https://github.com/TYPO3/typo3/blob/main/typo3/sysext/core/Classes/Resource/Rendering/VimeoRenderer.php#L136-L137):

protected function createVimeoUrl(array $options, FileInterface $file)
    {
        [$videoId, $videoHash] = explode('/', $this->getVideoIdFromFile($file), 2);

        $urlParams = [];

        if (!empty($videoHash)) {
            $urlParams[] = 'h=' . $videoHash;
        }

        // Rest of the method remains unchanged.
    }

I came to a similar solution:

         $videoId = $this->getVideoIdFromFile($file);
         $urlParams = [];
+        if (str_contains($videoId, '/')) {
+            [$videoId, $privateId] = explode('/', $videoId, 2);
+            $urlParams[] = 'h=' . htmlspecialchars($privateId);
+        }
         if (!empty($options['autoplay'])) {
             $urlParams[] = 'autoplay=1';
         }

Patch set 2 for branch main of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/77609

Patch set 3 for branch main of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/77609

Patch set 4 for branch main of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/77609

Patch set 5 for branch main of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/77609

Patch set 1 for branch 12.4 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/81070