Permanently Deleted Photos & Videos

The recently Deleted album is the only safety line offered by Photos. Once you have removed the photos from Recently Deleted, they are gone. Then you have to use the backups you made while you still had the photos. What kind of backups are you keeping? It will depend on the kind of backup you are keeping and on your use of iCloud Photos, if your backup includes the photos or not.

• If you are not using iCloud Photos, the iCloud backup of your iPhone will include the photos, also the backup on a computer.
• If you are using iCloud Photos, the iCloud backup of your iPhone will not include the photos, but the backup on a computer may include some of the photos.

If you have a backup with photos, you can recover them by restoring the iPhone from the backup Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

More details here: How to back up an iPhone, iPad, iPod Touch be able to Recover Accidentally, Permanently Deleted Photos - Apple Community

Permanently means exactly that: there is no way to recover this material. Only possible hope: do you have a back up that contains this material?