@Andi_Ireland Are any errors picked up in Picture Test? Go to Settings-Support-Self Diagnosis-Picture Test and follow instructions. If the picture Test fails would indicates fault, if not would need to initially check connections/cables.
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB One Ui 5.1,Android 13 .