It looks like the lens shading really is the issue here. The effect is stronger for your phone’s camera then it is for my Pixel 4a.
This copy of the dng has had the lens shading correction applied, and should work in dt or rt. I made it with the script described in this post. IMG_20210512_120109_pp.dng (22.0 MB)
Currently the only open source raw processor that can apply the lens shading correction internally is ART. It has to be enabled manually - in the Raw tab enable Flat-Field and select “Embedded in metadata”.
This plot shows what the lens shading map for each color looks like for your image:
The plot in the lower right shows the gain for the R G and B channels along a diagonal line drawn from one corner of the image to the other. In the center R = G = B, but at the edges R > G and R > B, which explains why the image has a blue-green color cast when the correction is not applied.