I have some samples from an X-T3 and an X-T4 that I can look at. I can try to look at X-T2 samples from @sguyader as well. It should be the same as the X-T20, but we should verify.
I assume that long exposure noise reduction must be turned off in the camera settings for these samples. I don’t know if ISO will make any difference at all for these cameras (invariant).
I cannot promise I will be able to look at this as soon as tonight. The forecast shows a clear sky.