Well, I don't know well about deb packaging, but:
Versions of packages xscreensaver suggests: ii firefox [www-browser] 109.0-1 pn fortune <none> pn gdm3 | kdm-gdmcompat <none> ii lynx [www-browser] 2.9.0dev.12-1 ii palemoon [www-browser] 32.0.0-1.gtk2 pn qcam | streamer <none> pn xdaliclock <none> pn xfishtank <none> pn xscreensaver-data-extra <none> pn xscreensaver-gl <none> pn xscreensaver-gl-extra <none>
As far as I googled, "pn" means that the package is "purged and not installed", so (unless I am wrong) this means that xscreensaver-gl is not installed. On the other hand, this seems to be saying: https://sources.debian.org/src/xscreensaver/6.06%2Bdfsg1-2/debian/xscreensaver-gl.install.stub/ that xscreensaver-gl-visual binary is in xscreensaver-gl. So maybe xscreensaver-gl-visual binary does not exist on system at the first place??
