SpamAssassin is clearly not intended for use by mail clients, as
evidenced by the number of backflips Evolution's SA module still has to
do just to detect the presence and nature of a running spamd (a problem
which D-Bus solved a decade ago), and recent SA developer comments.

In lieu of removing SA support entirely, remove all the crazy GSettings
that are (thankfully) not exposed in the UI and relegate Evolution's SA
integration to only the most basic usage (spamassassin / sa-learn).

Users are better off with Bogofilter anyway.  Leave SpamAssassin for
mail servers.