emelFM is apparently a very dead project, as it doesn't seem to have been updated since 2000, but still an excellent and idiosyncratic file manager that compiles cleanly on a modern Slackware (and, presumably, most any distro).
It is the only - or one of the extremely few - file managers that is (1) graphical, (2) dual-pane, (3) drag'n'drop, and (4) without icons. It has customizable buttons centered between the panes, configurable popup menus, and a configurable section of buttons by the command output window.
The README states it's basically a compilation of other apps' features and thanks
but it selects and combines these features in interesting ways. It's also user-extensible. For instance, xxdiff can be seamlessly turned into an emelFM button with the files to be diffed selected from each pane, simply by creating a button and defining it as '/path/to/xxdiff %f %F'.