recyclarr: add fallback SD qualities for old shows

services/arr/recyclarr.nix

@@ -173,6 +173,19 @@ in
                 ];
               }
               { name = "HDTV-720p"; }
+              # SD fallback for shows that predate HD or whose only seeded
+              # public-tracker copies are 480p/DVD/SDTV. Sonarr will still
+              # upgrade to WEB/Bluray (cutoff above) when an HD release
+              # surfaces.
+              {
+                name = "SD";
+                qualities = [
+                  "WEBDL-480p"
+                  "WEBRip-480p"
+                  "DVD"
+                  "SDTV"
+                ];
+              }
             ];
           }
         ];