I still have not had time to go 19.10 What does this show please?
dpkg -l | grep saver
me on 19.04
ii mate-screensaver 1.20.3-3 amd64 MATE screen saver and locker
ii mate-screensaver-common 1.20.3-3 all MATE screen saver and locker (common files)
apt search xscreensaver
has a number of hits.