Dual graphic card not working

I bought a riser to plug in my old graphics card because I want to create a virtual machine with a passthroug GPU.

I plugged everything in, and connected 1 screen to each graphics card.

But after the loading screen, the screen goes black. I have the impression that the OS launched well, but that GNOME may have crashed, because when I plug in a USB key, I get the audio notification. I’ve tried booting my PC with Ubuntu (live USB), and it works normally.

Why does Manjaro not seem to appreciate that I’ve added a 2nd graphics card?

PS: My graphics card is an AMD RX 5500 XT and my old one is an AMD HD7850.

Without some logs or something we cant possibly know.

Maybe begin with

inxi -Farz

and

mhwd -li -l

inxi -Farz

System:
  Kernel: 6.11.11-1-MANJARO arch: x86_64 bits: 64 compiler: gcc v: 14.2.1
    clocksource: tsc avail: hpet,acpi_pm
    parameters: BOOT_IMAGE=/boot/vmlinuz-6.11-x86_64
    root=UUID=9e5cc673-4721-4191-a136-bf87f8492cae rw quiet splash apparmor=1
    security=apparmor resume=UUID=b4352003-c003-4b4a-8c14-e1c778e83ba9
    udev.log_priority=3
  Desktop: GNOME v: 47.2 tk: GTK v: 3.24.43 wm: gnome-shell
    tools: gsd-screensaver-proxy dm: GDM v: 47.0 Distro: Manjaro
    base: Arch Linux
Machine:
  Type: Desktop Mobo: ASUSTeK model: PRIME B450M-A v: Rev X.0x
    serial: <superuser required> part-nu: SKU uuid: <superuser required>
    UEFI: American Megatrends v: 4401 date: 09/04/2023
CPU:
  Info: model: AMD Ryzen 5 2600 bits: 64 type: MT MCP arch: Zen+ gen: 1+
    level: v3 note: check built: 2018-21 process: GF 12nm family: 0x17 (23)
    model-id: 8 stepping: 2 microcode: 0x800820D
  Topology: cpus: 1x dies: 1 clusters: 1 cores: 6 threads: 12 tpc: 2
    smt: enabled cache: L1: 576 KiB desc: d-6x32 KiB; i-6x64 KiB L2: 3 MiB
    desc: 6x512 KiB L3: 16 MiB desc: 2x8 MiB
  Speed (MHz): avg: 3848 min/max: 1550/3850 boost: disabled scaling:
    driver: acpi-cpufreq governor: schedutil cores: 1: 3848 2: 3848 3: 3848
    4: 3848 5: 3848 6: 3848 7: 3848 8: 3848 9: 3848 10: 3848 11: 3848 12: 3848
    bogomips: 92428
  Flags: avx avx2 ht lm nx pae sse sse2 sse3 sse4_1 sse4_2 sse4a ssse3 svm
  Vulnerabilities:
  Type: gather_data_sampling status: Not affected
  Type: itlb_multihit status: Not affected
  Type: l1tf status: Not affected
  Type: mds status: Not affected
  Type: meltdown status: Not affected
  Type: mmio_stale_data status: Not affected
  Type: reg_file_data_sampling status: Not affected
  Type: retbleed mitigation: untrained return thunk; SMT vulnerable
  Type: spec_rstack_overflow mitigation: Safe RET
  Type: spec_store_bypass mitigation: Speculative Store Bypass disabled via
    prctl
  Type: spectre_v1 mitigation: usercopy/swapgs barriers and __user pointer
    sanitization
  Type: spectre_v2 mitigation: Retpolines; IBPB: conditional; STIBP:
    disabled; RSB filling; PBRSB-eIBRS: Not affected; BHI: Not affected
  Type: srbds status: Not affected
  Type: tsx_async_abort status: Not affected
Graphics:
  Device-1: Advanced Micro Devices [AMD/ATI] Navi 14 [Radeon RX 5500/5500M /
    Pro 5500M] vendor: ASRock driver: amdgpu v: kernel arch: RDNA-1
    code: Navi-1x process: TSMC n7 (7nm) built: 2019-20 pcie: gen: 4
    speed: 16 GT/s lanes: 16 ports: active: DP-3,HDMI-A-1 empty: DP-1,DP-2
    bus-ID: 0a:00.0 chip-ID: 1002:7340 class-ID: 0300
  Display: wayland server: X.org v: 1.21.1.14 with: Xwayland v: 24.1.4
    compositor: gnome-shell driver: gpu: amdgpu display-ID: 0
  Monitor-1: DP-3 model: HP L1908w serial: <filter> built: 2008
    res: 1440x900 dpi: 89 gamma: 1.2 size: 410x256mm (16.14x10.08")
    diag: 483mm (19") ratio: 16:10 modes: max: 1440x900 min: 720x400
  Monitor-2: HDMI-A-1 model: Samsung SyncMaster serial: <filter> built: 2008
    res: 1440x900 dpi: 89 gamma: 1.35 size: 410x257mm (16.14x10.12")
    diag: 484mm (19.1") ratio: 16:10 modes: max: 1440x900 min: 720x400
  API: EGL v: 1.5 hw: drv: amd radeonsi platforms: device: 0 drv: radeonsi
    device: 1 drv: swrast gbm: drv: kms_swrast surfaceless: drv: radeonsi
    wayland: drv: radeonsi x11: drv: radeonsi
  API: OpenGL v: 4.6 compat-v: 4.5 vendor: amd mesa v: 24.2.8-arch1.1
    glx-v: 1.4 direct-render: yes renderer: AMD Radeon RX 5500 XT (radeonsi
    navi14 LLVM 18.1.8 DRM 3.59 6.11.11-1-MANJARO) device-ID: 1002:7340
    memory: 7.81 GiB unified: no display-ID: :0.0
  Info: Tools: api: eglinfo,glxinfo x11: xprop,xrandr
Audio:
  Device-1: Advanced Micro Devices [AMD/ATI] Navi 10 HDMI Audio
    driver: snd_hda_intel v: kernel pcie: gen: 4 speed: 16 GT/s lanes: 16
    bus-ID: 0a:00.1 chip-ID: 1002:ab38 class-ID: 0403
  Device-2: Advanced Micro Devices [AMD] Family 17h HD Audio vendor: ASUSTeK
    driver: snd_hda_intel v: kernel pcie: gen: 3 speed: 8 GT/s lanes: 16
    bus-ID: 0c:00.3 chip-ID: 1022:1457 class-ID: 0403
  API: ALSA v: k6.11.11-1-MANJARO status: kernel-api with: aoss
    type: oss-emulator tools: alsactl,alsamixer,amixer
  Server-1: JACK v: 1.9.22 status: off tools: N/A
  Server-2: PipeWire v: 1.2.7 status: active with: 1: pipewire-pulse
    status: active 2: wireplumber status: active 3: pipewire-alsa type: plugin
    tools: pactl,pw-cat,pw-cli,wpctl
Network:
  Device-1: Realtek RTL8111/8168/8211/8411 PCI Express Gigabit Ethernet
    vendor: ASUSTeK RTL8111H driver: r8169 v: kernel pcie: gen: 1
    speed: 2.5 GT/s lanes: 1 port: f000 bus-ID: 07:00.0 chip-ID: 10ec:8168
    class-ID: 0200
  IF: enp7s0 state: up speed: 1000 Mbps duplex: full mac: <filter>
  IF-ID-1: br-3709cb048292 state: down mac: <filter>
  IF-ID-2: docker0 state: down mac: <filter>
  Info: services: httpd, NetworkManager, systemd-timesyncd, wpa_supplicant
Drives:
  Local Storage: total: 12.04 TiB used: 9.36 TiB (77.7%)
  SMART Message: Required tool smartctl not installed. Check --recommends
  ID-1: /dev/sda maj-min: 8:0 vendor: LDLC model: N/A size: 223.57 GiB
    block-size: physical: 512 B logical: 512 B speed: 6.0 Gb/s tech: SSD
    serial: <filter> fw-rev: 2A0 scheme: GPT
  ID-2: /dev/sdb maj-min: 8:16 vendor: Western Digital
    model: WD40PURZ-85AKKY0 size: 3.64 TiB block-size: physical: 4096 B
    logical: 512 B speed: 6.0 Gb/s tech: HDD rpm: 5400 serial: <filter>
    fw-rev: 0B80 scheme: GPT
  ID-3: /dev/sdc maj-min: 8:32 vendor: Seagate model: ST8000DM004-2U9188
    size: 7.28 TiB block-size: physical: 4096 B logical: 512 B speed: 6.0 Gb/s
    tech: HDD rpm: 5400 serial: <filter> fw-rev: 0001
  ID-4: /dev/sdd maj-min: 8:48 vendor: Western Digital
    model: WDS100T2B0A-00SM50 size: 931.51 GiB block-size: physical: 512 B
    logical: 512 B speed: 6.0 Gb/s tech: SSD serial: <filter> fw-rev: 20WD
    scheme: GPT
Partition:
  ID-1: / raw-size: 214.47 GiB size: 210.05 GiB (97.94%)
    used: 170.46 GiB (81.2%) fs: ext4 dev: /dev/sda2 maj-min: 8:2
  ID-2: /boot/efi raw-size: 300 MiB size: 299.4 MiB (99.80%)
    used: 292 KiB (0.1%) fs: vfat dev: /dev/sda1 maj-min: 8:1
Swap:
  Kernel: swappiness: 60 (default) cache-pressure: 100 (default) zswap: no
  ID-1: swap-1 type: partition size: 8.8 GiB used: 0 KiB (0.0%) priority: -2
    dev: /dev/sda3 maj-min: 8:3
Sensors:
  System Temperatures: cpu: 43.2 C mobo: N/A gpu: amdgpu temp: 51.0 C
    mem: 0.0 C
  Fan Speeds (rpm): N/A gpu: amdgpu fan: 0
Repos:
  Packages: 1689 pm: pacman pkgs: 1612 libs: 463
    tools: gnome-software,pamac,yay pm: flatpak pkgs: 77
  Active pacman repo servers in: /etc/pacman.d/mirrorlist
    1: https://forksystems.mm.fcix.net/manjaro/stable/$repo/$arch
    2: https://mirror.bouwhuis.network/manjaro/stable/$repo/$arch
    3: https://mirror.kamtv.ru/manjaro/stable/$repo/$arch
    4: https://mirror.math.princeton.edu/pub/manjaro/stable/$repo/$arch
    5: https://mirrors2.manjaro.org/stable/$repo/$arch
    6: https://mirror.archlinux.tw/Manjaro/stable/$repo/$arch
    7: https://gsl-syd.mm.fcix.net/manjaro/stable/$repo/$arch
    8: http://mirror.is.co.za/mirrors/manjaro.org/stable/$repo/$arch
Info:
  Memory: total: 48 GiB available: 46.96 GiB used: 8.5 GiB (18.1%)
  Processes: 382 Power: uptime: 1h 42m states: freeze,mem,disk suspend: deep
    avail: s2idle wakeups: 0 hibernate: platform avail: shutdown, reboot,
    suspend, test_resume image: 18.76 GiB services: gsd-power,
    power-profiles-daemon, upowerd Init: systemd v: 256 default: graphical
    tool: systemctl
  Compilers: clang: 18.1.8 gcc: 14.2.1 Shell: Zsh v: 5.9
    running-in: gnome-terminal inxi: 3.3.37

mhwd -li -l

> Installed PCI configs:
--------------------------------------------------------------------------------
                  NAME               VERSION          FREEDRIVER           TYPE
--------------------------------------------------------------------------------
           video-linux            2024.05.06                true            PCI


Warning: No installed USB configs!
> 0000:0a:00.0 (0300:1002:7340) Display controller ATI Technologies Inc:
--------------------------------------------------------------------------------
                  NAME               VERSION          FREEDRIVER           TYPE
--------------------------------------------------------------------------------
           video-linux            2024.05.06                true            PCI
     video-modesetting            2020.01.13                true            PCI
            video-vesa            2017.03.12                true            PCI


> 0000:07:00.0 (0200:10ec:8168) Network controller Realtek Semiconductor Co., Ltd.:
--------------------------------------------------------------------------------
                  NAME               VERSION          FREEDRIVER           TYPE
--------------------------------------------------------------------------------
         network-r8168            2023.09.12                true            PCI

This kernel is EOL since December 2024 (this may be unrelated, or it may be the problem itself)

Please replace it with 6.12

I have updated the kernel and the system, everything is up-to-date. But still both screen remain black.

Edit: Even with a Live USB, Manjaro doesn’t seem to handle dual graphics cards… Does anyone know if it’s possible to use 2 graphics cards on Manjaro? I don’t want to go back to Ubuntu for that … Manjaro is the first OS that doesn’t become unstable after 1 year ( I’m on Manjaro for 3 years now)