X2Go's “X Server” is called “nxagent”. It is part of the nx-libs package.

As of version 3.5.0.x, nxagent is forked from the X.org 6.9 codebase (from 2005) feature-wise (but not security-wise, where it is at much newer level). Therefore, there are multiple reasons why certain modern “3d-ish” desktops are incompatible with nxagent, and therefore X2Go.

• The desktop environment requires the X11 extension “Xcomposite”, which nxagent 3.5.0.x and X.org 6.9 do not support.
• The desktop environment requires a newer version of the X11 extension “GLX” (OpenGL) than nxagent 3.5.0.x and X.org 6.9 provide (version 1.2). Note: there's a workaround for this: glx-xlib-workaround
• The desktop environment requires a newer version of the X11 extension “XRANDR” than nxagent 3.5.0.x provides (version 1.2).nxagent offers “XRANDR” 1.5 now, so this no longer a problem.
• The desktop environment checks for a specific physical graphics driver, but nxagent doesn't use physical graphics adapters/drivers.

Ultimately, addressing issues #1 and #2 requires a lot of work. Solutions are discussed here.

It is recommended to switch to using a compatible desktop environment if your desktop environment is listed below as incompatible.

• LXDE (not LXQt)
• XFCE

/usr/bin/xfconf-query -c xfwm4 -p /general/use_compositing -s false

• MATE

• IceWM

In X2Go Client, you must specify the Session Type as: Custom Desktop: icewm-session

• OpenBox

In X2Go Client, You must specify the Session Type as: Custom Desktop: openbox-session

• GNOME 2: Compatible and no workaround required
• GNOME 3.0 through 3.6: “GNOME Fallback Mode” must be installed. This is included with most, if not all distros.
• GNOME 3.8: “GNOME Flasback Mode” 3.8.x must be installed. It is seldom included with distros. There are bugs with it. Using GNOME 3.8 with X2Go is not recommended.
• GNOME 3.10: “GNOME Flasback Mode” 3.8.x may be compatible, but there are even more bugs with it. It is seldom included with distros. Using GNOME 3.10 with X2Go is not recommended.
• GNOME 3.12 and later: TBD, but probably not compatible. Using GNOME 3.12 and later with X2Go is not recommended.

• KDE 3: Compatible and no workaround required
• KDE 4: Compatible and no workaround required
• KDE 5: Incompatible due to plasmashell requiring GLX 1.3 We have received several reports that KDE 5 now works with X2Go, even though it takes a long time to initialize the session. If you're interested in running KDE 5 via X2Go and run into issues, please join the X2Go-User Mailing List or, if you are certain you've found a bug, subscribe to X2Go-Dev and file a bug report.

For better performance you should set Backend=XRender and GraphicsSystem=native and XRenderSmoothScale=false in the [Compositing] section of the kwinrc (usually residing in .kde/share/config).

1. Ubuntu 12.04: Compatible, as long as package “unity-2d” is installed. By default with “Ubuntu Desktop”, it is.
2. Ubuntu 12.10 and later (including 14.04): Not compatible

1. Cinnamon 1.4 (Linux Mint 13 “Maya”): Compatible, you must specify the Session Type as: Custom Desktop: gnome-session-cinnamon
2. Cinnamon 2.2 (Linux Mint 17 “Qiana”): Not compatible. Cinnamon reverts to “fallback mode”, which is not as good as regular “cinnamon” nor “cinnamon2d”. If you wish try try it in anyway, specify the Session Type as: Custom Desktop: cinnamon-session-cinnamon2d

Compatibility issues with Cinnamon are being tracked in bug 150

1. LXQt due to Qt5 incompatibility

1. E17 (Bodhi Linux 24.0, “enlightenment” package version: 20130818-1)

In X2Go Client, You must specify the Session Type as: Custom Desktop: /usr/bin/enlightenment_start

However, bug 555 (Windows cannot be moved by dragging) was encountered, and not much testing has been done.