Hi @ap1
Welcome to pixels and darktable.
Here is a new user’s guide from @Donatzsky
Regarding clipping, are you using the clipping indication icon at the bottom-right of the darktable? There are options to set there by right-clicking. My personal preference is to set the clipping preview mode to “luminence only.” But mostly I avoid using it. Some folks say that a little saturation clipping is ok in most cases. For the umbrellas in the photo here, the temptation is to push saturation hard. 
I prefer to look at scopes - waveform for luminance and vectorscope for colors.