Clarinets in D are sopranino clarinets, not soprano clarinets. However, in Dorico, D Clarinet is found under “Soprano Clarinet” instead of “Sopranino Clarinet.”
I don’t pretend to be an expert on clarinets, but for what it’s worth Wikipedia says this classification is not universal, and the standard text we use to help us with these decisions (Stiller’s “Handbook of Instrumentation”) doesn’t list the D soprano/sopranino clarinet.
AFAIK they are now obsolete, though a few early 20th century composers used them in orchestral scores (e.g. the Rite of Spring, IIRC).
Basically the D and Eb clarinets were a pair like the A and Bb.
Like the A clarinet, the D never had a use in wind bands, which is the commonest habitat of the Eb - who wants to carry two instruments around when marching?
I wouldn’t say obsolete - just rare. They are more common in the EU, especially those countries where the German system clarinet is used.
Rite of Spring, Schoenberg Chamber Symphony No.1 and several R. Strauss works use the D clarinet. Also, many players use it for the second suite of Daphnis and Chloe as the original E-flat part hovers around B major.