We found the record label search option on the QoBuz "web player", but it is not available on the QoBuz mobile app (I could not find it).
The Qobuz mobile app has a feature that isn't adequate for a search, but might be useful for some small labels — you can bring up a list of the entire catalog of a record label. Open any album from the record label you're interested in, and scroll down to the bottom of the track list. You will see "Recorded by", followed by the name of the record label, which is a hotlink. If you tap on it, it brings up all the albums of the record label. Even a small record label may have several hundred albums, so this really more for browsing than searching.