For a camera card you can still enable the "select the “Delete items” tick box below the toolbar. (Import photos from a camera or phone using Photos on Mac – Apple Support (UK)) It will depend on your camera model, if the option is available, however:
- "If you want to delete photos from the camera after importing them, select the “Delete items” tickbox.
- This option does not appear for all cameras."
But you have to do it, before you start the import from the card. This is risky, because the items will be deleted from the card, before we can check, if there have been transmission errors. The photos will be deleted from the card, sight unseen. We cannot repeat the import, if Photos should crash, when indexing the new photos in the library or if some photos are showing a corruption.
I stopped using this feature years ago, after having seen in these forums, that quite a few users have lost precious photos to "Delete after import". I am now erasing the card in the camera only after the import has finished, after I have looked at all originals, not just the thumbnails, and I am having made the first backup copy of the imported photos.
Which camera model are you using? It would be good to know, which cameras are still supporting this feature.