Merci pour ta suggestion, il y a du mieux !!!!!!

Direct rendering fonctionne: j'ai installé nvidia-settings, puis coché "Include X display name in the config file", et çà a fonctionné, mais seulement sur l'ordi "en direct"; via export display, par contre, çà ne fonctionne pas.

Au lancement de nvidia-settings via xdmcp (export display), j'ai toutes sortes de messages d'erreurs (voir ci-après).

En revanche, quand je suis direct sur la machine, le direct rendering fonctionne désormais; donc, merci pour la suggestion ;-)

Erreurs Nvidia via export XDMCP :

ERROR: Unable to assign attribute DigitalVibrance specified on line 18 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute ImageSharpening specified on line 19 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute SyncToVBlank specified on line 20 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute AllowFlipping specified on line 21 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute LogAniso specified on line 22 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute FSAA specified on line 23 of configuration
file '/home/juju35/.nvidia-settings-rc' (no Display connection).
ERROR: Unable to assign attribute TextureSharpen specified on line 24 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute ForceGenericCpu specified on line 25 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute CursorShadow specified on line 26 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute CursorShadowXOffset specified on line 27 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute CursorShadowYOffset specified on line 28 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute CursorShadowAlpha specified on line 29 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute CursorShadowRed specified on line 30 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute CursorShadowGreen specified on line 31 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute CursorShadowBlue specified on line 32 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute FSAAAppControlled specified on line 33 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute LogAnisoAppControlled specified on line 34 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute RedBrightness specified on line 35 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute GreenBrightness specified on line 36 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute BlueBrightness specified on line 37 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute RedContrast specified on line 38 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute GreenContrast specified on line 39 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute BlueContrast specified on line 40 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute RedGamma specified on line 41 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute GreenGamma specified on line 42 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute BlueGamma specified on line 43 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute OpenGLImageSettings specified on line 44 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute XVideoTextureSyncToVBlank specified on line
45 of configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute XVideoBlitterSyncToVBlank specified on line
46 of configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: Unable to assign attribute XVideoSyncToDisplay specified on line 47 of
configuration file '/home/juju35/.nvidia-settings-rc' (no Display
connection).
ERROR: NV-CONTROL extension version 1.6 is too old; the minimimum required
version is 1.9.
ERROR: Unable to determine number of NVIDIA GPUs on 'debian:1.0'.
ERROR: Unable to determine number of NVIDIA Frame Lock Devices on
'debian:1.0'.