In Lubuntu 17.04 (zesty) the file manager (pcmanfm) no longer lists other partitions/volumes on the computer. It's perplexing, because they used to be there in the sidebar (under a heading of something like "Other places"). They wouldn't be mounted, but clicking them would mount them. In my experience, this is the usual on Ubuntu and Lubuntu. Currently though, it's not there, despite the option for it being turned on in the preferences, and I don't know how to get it back.
I can still see the other partitions with Gparted,
fdisk etc. etc. and mount them via the terminal if I wish. But I want to browse them with the GUI too.
I have searched online for any solutions to no avail. I have also at this point switched through several file managers as well as entire windows managers and desktop environments and the only one that displayed the other volumes again was KDE Plasma, but I want to be able to use a nice minimal environment like LXDE (Lubuntu default).
How can I get other partitions to show up in the file manager on Lubuntu 17.04?