Enable PseudoColor visuals in Xorg

I am trying to run an old X11 application that requires PseudoColor visuals on a newer Linux workstation. The workstation does not advertise any PseudoColor visuals through xdpyinfo. Only TrueColor and DirectColor are available. Is there a way to enable 8-bit PseudoColor visuals? I tried setting the default depth to 8 in xorg.conf, but that prevented Xorg from starting, and is not the mode we want to run in by default.

Workstation is x86_64 running RHEL 7.9 and has a Nvidia Quadro P2200 card. Nvidia driver version is 440.82.

I’d rather try to run it within xephyr.

Thanks. I’ll look into it. Installing xephyr might not be an option for us, though.

Only other method is enabling color index overlay in xorg.conf and hope your legacy application is happy with that. The downside is this won’t work with compositing enabled so won’t work with gnome and other compositing window managers. Don’t know either if cioverlay are about to stay going forward.