Profiled denoise results are very different between preview and exported image
On preview (as seen on screenshot) there's almost no residual noise.
After exporting, lots of noise are visible in exported image, especially in darker areas.
Demosaic method doesn't make any difference (tried ppg and amaze), disabling OpenCL also doesn't change anything.
In this case denoise profile is taken from https://github.com/darktable-org/darktable/pull/1471 — however, I noticed that it doesn't matter which profile is used, the noise reduction in preview is always much stronger than in exported image.