Here’s my take on this.
Once a video is permanently deleted from the Google Photos trash, direct recovery from Google’s servers is highly unlikely. It’s designed to be a final step. However, there are a couple of angles to consider before giving up.
On one hand, the file might still exist on your S21’s local storage if it hadn’t been overwritten yet. You could look into Android data recovery software for this. These tools scan the device’s internal memory for file fragments. Success rates vary wildly, but it’s a potential avenue.
On the other hand, it’s worth double-checking other potential backup locations. Since you have a Samsung device, see if Samsung Cloud or another service was automatically backing up your gallery. Sometimes we have redundant backups we forget about.