In your sheet, click Extensions, then Remove Duplicates, and choose: Find Duplicates or Uniques. Follow the steps in the add-on wizard to choose the range and columns you'd like to check for ...

Highlight the entire row if duplicates are in one Google Sheets column. Highlight duplicate cells in multiple Google Sheets columns. Highlight actual duplicates, leaving the 1st instance.

In iOS 16, however, that's no longer the case, because the Photos app will now automatically detect any duplicates in your library and collate them together for your inspection.