xfce4-panel >= 4.17.2 - Urgency blinking not properly rendered in tasklist

This requires the "suggested-action" CSS class to be rendered properly, which is apparently not the case. The Orchis theme also suffers from this, for example, but it works fine with Adwaita.
Related commit: https://gitlab.xfce.org/xfce/xfce4-panel/-/commit/9ea5f4e35e1bdb75654b0998b123b19c70388d4b
Related forum thread: https://forum.xfce.org/viewtopic.php?id=16789