Comment # 26 on bug 1177395 from Chris Schaller

(In reply to Jonathan Kang from comment #25)
> (In reply to Chris Schaller from comment #24)
> > Wait a moment.  Shouldn't GNOME_SOFTWARE_PLUGINS_BLOCKLIST=fwupd disable
> > fwupd?
> > 
> > gnome-software still lists the plugin as enabled:
> > 
> > chris@linux:~/gs-issues> pkill gnome-software;
> > GNOME_SOFTWARE_PLUGINS_BLOCKLIST=fwupd gnome-software
> > 17:00:26:0724 Gs  enabled plugins: desktop-categories, fwupd, os-release,
> > packagekit, packagekit-local, packagekit-offline, packagekit-proxy,
> > packagekit-refine-repos, packagekit-refresh, packagekit-upgrade,
> > packagekit-url-to-app, shell-extensions, appstream, desktop-menu-path,
> > flatpak, hardcoded-blacklist, hardcoded-featured, hardcoded-popular,
> > modalias, packagekit-refine, rewrite-resource, odrs, packagekit-history,
> > provenance, systemd-updates, generic-updates, provenance-license, icons,
> > key-colors, key-colors-metadata
> > 17:00:26:0724 Gs  disabled plugins: dpkg, dummy, fedora-pkgdb-collections,
> > fedora_langpacks, repos, epiphany
> > 
> > fwupd also shows up in my logs.
> 
> That's weird. I added `GNOME_SOFTWARE_PLUGINS_BLOCKLIST=fwupd` to
> collect.sh, and
> it shows fwupd as disabled plugin.

Did you try this on Leap 15.2?
I confirmed with two Leap 15.2 installations that the
GNOME_SOFTWARE_PLUGINS_BLOCKLIST is getting ignored on both.
Whereas on my Tumbleweed system it got respected.