Good morning,

We're building a compute cluster using Dell rackmounts and ubuntu 24.04. Generally, the install is going well, but OpenGL is not.

The machines are multi-user, and users can connect using x2go (preferred) or vnc in order to get graphical logins. Our previous cluster was running CentOS and the OpenGL worked a treat, however on these new machines I get the dreaded 'Error: couldn't get an RGB,, Double-buffered visual' from glxgears, and glxinfo spits out:
name of display: :50
Error: couldn't find RGB GLX visual or fbconfig

From an x2go session:

inxi -F shows this:
Graphics:
Device-1: Matrox Systems G200eR2 driver: mgag200 v: kernel
Display: server: X.Org v: 0.0 driver: X: loaded: modesetting gpu: mgag200
resolution: 1456x902~60Hz
API: EGL v: 1.5 drivers: swrast platforms: x11,surfaceless,device
API: OpenGL v: 4.5 vendor: mesa v: 24.0.9-0ubuntu0.2 note: incomplete
(EGL sourced) renderer: llvmpipe (LLVM 17.0.6 256 bits)


Which suggests that the mesa drivers might be at fault, and the X.org v: of 0.0 looks suspicious.

A vnc session to same machine gives different data (although still fails to work)
Graphics:
Device-1: Matrox Systems G200eR2 driver: mgag200 v: kernel
Display: server: X.Org v: 1.21.1.11 driver: X: loaded: modesetting gpu: mgag200
s-res: 1024x768
API: EGL v: 1.5 drivers: swrast platforms: x11,surfaceless,device
API: OpenGL v: 4.5 vendor: mesa v: 24.0.9-0ubuntu0.2 note: incomplete
(EGL sourced) renderer: llvmpipe (LLVM 17.0.6 256 bits)

The difference is in the Display line as one would expect. I've had a look at the mesa drivers and the dependencies look alright (from 'apt depends mesa-common-dev') It feels like I might be missing something obvious, but ...
in any case, just for completeness:
6.8.0-48-generic #48-Ubuntu SMP PREEMPT_DYNAMIC
PRETTY_NAME="Ubuntu 24.04.1 LTS"
NAME="Ubuntu"
VERSION_ID="24.04"
VERSION="24.04.1 LTS (Noble Numbat)"
VERSION_CODENAME=noble
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=noble
LOGO=ubuntu-logo

Any pointers will be gratefully accepted.

Jeff, MRC-CBSU