NPAPI plug-in support is slated for removal from the #WebKitGTK and #WPE ports. The 2.28.x versions (the current stable series) still support it, and will have at least six more months of security updates. Then starting with 2.30.0, due March 2021, NPAPI will be gone for good.
More info: https://perezdecastro.org/2020/webkitgtk-npapi-sunsetting.html
Ouch, I'm half asleep: the current stable releases are 2.30.x (still with NPAPI support), and the 2.32.x due in March 2021 (which won't have it).