niri: maximize thunderbird

home/.config/niri/config.kdl

@@ -103,6 +103,14 @@ window-rule {
     }
 }
 
+window-rule {
+    match app-id=r#"^thunderbird$"#
+    open-maximized true
+    focus-ring {
+        off
+    }
+}
+
 // Open the Firefox picture-in-picture player as floating by default.
 window-rule {
     // This app-id regular expression will work for both: