After further investigation, although I can invoke a terminal window while running the standard(?) Ubuntu window manager, none of my attempts to replace that window manager with ctwm have worked. I've been able to launch various configurations of ctwm using examples found online, but none of them allow me to open xterm or similar windows in any of the workspaces, which I have been doing for many years using ctwm running on fedora.
The xterm-like programs exist and I can run them in standard ubuntu 'desktops' which I wish to replace with ctwm. I hope there's something simple that I've missed that will allow me to launch terminal windows while running ctwm. as window manager, with a 3x4 array of virtual desktops. Any ideas? Later, I also hope to be able to run zoom on ubuntu, which I have not yet tried. Aaron