Package: gdm3 Version: 43.0-3 The machine in question has two graphic chips: - ASPEED AST2500 64MB built into the motherboard and - NVIDIA GeForce GTX 1660 Ti PCIe graphics card. The ASPEED chip (/dev/dri/card0) has only a VGA port; nothing is connected to this D-SUB port. The NVIDIA card (/dev/dri/card1) has lots of ports; a properly functioning monitor Philips 275B1 is connected to the DisplayPort of the card, and the other ports are empty. In the journal we see a warning and an error written there during boot: /usr/libexec/gdm-x-session[…]: (WW) Warning, couldn't open module ast /usr/libexec/gdm-x-session[…]: (EE) Failed to load module "ast" (module does not exist, 0) From a user's viewpoint, there's probably no error here and nothing to warn about here, since the absence of anything connected to the VGA D-SUB port is fine as long as a functioning monitor is connected elsewhere (in our case, to the graphics card). I tried to specify the monitor as a command-line argument “video=DP-1:2560x1440R”; does this help or can this even be improved? If the (WW) and (EE) lines occur for a different reason than the absense of anything connected to the VGA D-SUB port, the reason should be visible in the journal (but it's not)! The machine has other, related issues (cf. #1040497), which, hypothetically, may (or may not) interplay with this one. The relevant parts of the journal and of the lshw and lspci outputs are attached. By the way, after boot and after gdm3+gnome started, the module ast turns out to be even loaded (probably, for no good reason!): # lsmod | grep ast ast 61440 1 drm_vram_helper 20480 1 ast drm_ttm_helper 16384 3 drm_vram_helper,ast,nouveau drm_kms_helper 204800 5 drm_vram_helper,ast,drm_display_helper,nouveau drm 614400 18 drm_kms_helper,drm_vram_helper,ast,drm_display_helper,drm_ttm_helper,ttm,nouveau i2c_algo_bit 16384 3 igb,ast,nouveau Gratefully, AlMa