While messing around with Lubuntu 19.04, running lxqt-sudo to launch Pluma text editor as root so that I could edit the /var/www PHP projects I had, I noticed when rightclicking the file browser pane and choosing View Folder, that it opened up, at first, PCManFM-Qt. However, when it did so, it used a very ugly theme. (That's another question I have posted.) Then, I installed Nautilus. When I did, now when I open Pluma as root, it uses some file manager called Files, which I assume is Nautilus because it shows up when I do
ps -ef | grep -i nautilus.
How do I tell Pluma to use PCManFM-Qt instead of Nautilus? What config file do I edit?