buildroot/board/beaglebone/rootfs_overlay/etc/qt5/eglfs_kms_cfg.json

{
  "device": "/dev/dri/card0",
  "hwcursor": false,
  "pbuffers": true,
  "outputs": [
    {
      "name": "VGA1",
      "mode": "off"
    },
    {
      "name": "HDMI1",
      "mode": "1024x768"
    }
  ]
}