Morton Feldman is a classical composer. I have around 15 albums on which he is the composer. However, when I search for Morton Feldman under composers, nothing is returned. Likewise, if I go to Compositions and search for Morton Feldman nothing is returned. I have double checked the metadata using Yate and he is always listed as a composer. If I do a general search for Feldman, all albums are returned, but Feldman is shown as an Artist.
When I tried the same search for Feldman, I also got some missing and unexpected results. I think it’s due to Roon’s confusion with composers who are are also listed as artists. I made two changes and things are working for me as expected.
Try selecting him as a Classical Composer in the Artist Editor.