I forgot to mention... GNUstep's recommended window manager is Window Maker, which is still alive and in active maintenance with new versions coming out.

There are lots of little Window Maker applets out there to choose from, so you can accessorize your GSDE (or NEXTSPACE) setup with wm-applets and docklets for volume, sound output, mic control, power management, and all those little fripperies that other desktops come with or can do.

A slight limitation is that GNUstep has its own dock and suggests disabling the Window Maker dock, but you can go the other way round and disable the dock provided by GNUstep Workspace and use the WM dock instead.

Also, it is worth mentioning that there is a new entrant in the "GNUstep based desktop environment" race: Gershwin.

https://github.com/gershwin-desktop

Currently only available in GhostBSD though.