Yeah. Do you have Halide or Pro Camera to use with jpeg or HEIC? Otherwise the only way to get the 48mp resolution from the default camera is to use ProRAW. If you want ProRAW, then go to settings, down to camera, select formats, then turn ProRAW on. Then you’ll have to edit that raw file to save as a jpeg.
As for Halide, (if ProRAW isn’t what you want) you enter the settings and go to capture and scroll down and select 48mp and HEIC or jpeg. From there Halide will take photos in 48mp resolution. This is the only way to get the 48mp outside of the default camera.