Nah, looks right. You have a single-band image with the default palette applied.
You can change the layer symbology to use another color ramp to mimic the appearance you see in WebODM. Or use another you may like better!
Incidentally, this is a great example of what I said above. This is data in a grid. The data values are roughly 420ish-570ish per pixel in this case. WebODM applies a color ramp to aide visual analysis. Same for QGIS. However, it doesn’t really look like anything on its own, and GIMP showed you data VS nodata, basically, since that was all it could display without a ramp/paletted interpretation.
Colors in most normal 8bit depth images are in the range of 0-255 (integer) for each band of Red, Green, and Blue, the composition of which gives you an RGB color value per pixel. So you can see why GIMP didn’t show you much, since it had a single band of crazy non-normal values. It really should stretch/palette to grayscale like QGIS does.
So, you can symbolize it in QGIS, or in WebODM you can export the symbolized image as a rendered GeoTiff, which is a great way to “burn in” your visualization to ensure others see it the exact same way. Note that this changes (or ruins, if you’re not being generous) the data. No longer suitable for numerical analysis.