When you first insert a Sd card in the phone it'll ask if you'd like the photos to go to the Sd card as default.
Or launch the Camera App and hit the cog ie settings and you can change the default place there @John49
Yes even tho the photo itself is in the Sd card it'll remain in the Gallery to view.
Current Phone ~
Samsung Note 20 Ultra 5G SM-N9860_256Gb SnapDragon 865+
Samsung One Ui 3.0/ Android 11.