@laoman
When I search for "Wagner Ring Cycle" in Roon, I count 29 album hits from the Qobuz service alone. On Qobuz, represented conductors include Daniel Barenboim (Bayreuth 1991), Karl Bohm (1967), Herbert von Karajan, George Solti (Nov 2014 performance on,Decca) Joseph Keilberth (July 1953 performance, 2021 HD mastering), Lorin Mazel, Wilhelm Furtwangler (1953 performance on Warner Classics), George Szell, James Levine (August 1994 on DG), and Zubin Mehta.
Certainly, not all classical music (or individual artists) will get equal coverage on all streaming services. Qobuz seems to be one of the most comprehensive for classical in general (dunno about Wagner in particular). And on Roon, I've seen recurring complaints about how well the search engine works (or does not work) for finding, displaying, and organizing classical music. The tech is still evolving, it seems.