How to recover permanently deleted photos from iPhone?

You cannot recover permanently deleted photos directly from the iPhone, only from the backups you made, before the photos became permanently deleted. Restore all content to iPhone from a backup

Once the photos are no longer in Recently Deleted, they are gone. Recently Deleted is the only safety line offered by Photos, as described here: How to recover deleted photos on your iPhone, iPad, Mac, or Apple Vision Pro - Apple Support Before you empty Recently Deleted, be careful to check it for accidentally deleted items that you still need.

What kind of backups are regularly making? You need a backup that includes the photos.

• The iCloud backup of your iPhone will include the photos, unless you are using iCloud Photos.
• If you are using iCloud Photos, you have to save the photos separately, see: About backups for iPhone, iPad, and iPod touch

Let's just go ahead and say it: iCloud is not a backup service. To recover using the Mobile Device iCloud Backup you have to erase everything on the phone since the last backup. That is great if your phone gets run over by a truck, or for transferring stuff to a new phone, but it's not so useful for unfortunate mistakes. On the other hand, iCloud Photos "synchronizes" its Photos Library with the phone, so what you see on the phone is what is at iCloud. iCloud Photos doesn't keep pictures in "Recently Deleted" any longer than the phone does.

Unfortunately, if you don't keep your own backups to an external drive, then there really isn't any place else to look. To back up your pictures you can just plug in an external drive, select the pictures, and use Share>Save to Files. Alternatively, you can backup to a computer:

Transfer photos and videos from your iPhone or iPad to your Mac or PC

If you haven't done one of those backups, then your remaining pictures continue to be in peril. 

léonie wrote:

The iCloud backup of your iPhone will include the photos, unless you are using iCloud Photos.

Even if you were making iCloud backups that included photos, new backups replace old ones.

With automatic backups on, it would not be long before a new backup that DIDN"T have any of the permanently deleted photos replaced the backup that did. Then, when you restored that new backup, you'd be wiping other data on the phone without getting any of the lost photos back.