Doesn't require a trigger word, but adding them to the prompt will help sharpen the background and make it look like an actual iphone photo, otherwise it serves as an all purpose realism enhancer and will make all images more natural.

For Flux, the trigger is "iphone photo".
For SD3.5 Large it's "iph0ne", try lower weight around 0.5.. first attempt at sd3.5, it might be bad.

Trained with Ostris's ai-toolkit: Github page

SD3.5 Large V2 Test version comparison - FLUX V1 vs V2 comparisons below

FLUX
V1 is iPhone Photo 6-2000 /// V2 is iPhone Photo 7-15000