if you want to keep using npapi browser plugins you might like to try the pale moon browser
mozilla firefox (and the other browsers) are discontinuing support for npapi plugins
oracle recommend java applets users try Java Web Start or Pale Moon
JWS apps don’t rely on a browser plugin, in many cases they can provide a migration path from Java Applets.
the pale moon browser roadmap says they will always support npapi
Pale Moon supports NPAPI plug-ins. Unlike Firefox, we will not be deprecating or removing support for these kinds of plug-ins. This means that you will be able to continue using your media, authentication, and other plug-ins in Pale Moon like Flash, Silverlight, bank-authenticators or networking plug-ins for specific purposes.