x11-libs/gtk+:2 is EOL and x11-libs/gtk+:3 was already used by default IUSE=+gtk3. That leaves IUSE=spell with dependency on app-text/gtkspell:2 which still pulls in x11-libs/gtk+:2.
No release since 2015 and no commit in upstream repo since 2017; missing icons in GTK3 release version; the build system in git master besides being horrible is broken in its current state.