@Popanz are the artifacts visible if you disable the “Flat field correction” (gainmaps) in rawprepare?
If I turn off “Flat field correction”, the artefacts are gone.
I looked at this image for a second time. I believe the DNG coming out of the camera is not a RAW file. It is processed and denoised already in the camera and doesn’t require denoising. Being a DNG it retains good flexibility for processing and if you like some additional sharpening presets in the diffuse or sharpen module could be applied to get sharper detail if desired. One issue I have with DNG files is it is difficult to know if it is truly a raw file or a file that has been processed but saved as a DNG as it could be either. But with your image I detected no noise issue even when looking at high magnification.