## Summary

Installing Omarchy 4.0.4 from the live ISO on an AMD-APU laptop (HP 255 G10,
Ryzen 7 7730U "Mendocino", AMI UEFI firmware) results in a black screen in
the live session. Root cause: the live ISO ships the `linux-t2` kernel
(Watanare T2 — the Apple T2/ASi kernel), which **contains no amdgpu driver
at all**, so on AMD hardware the live session can only use efifb/simpledrm
framebuffer passthrough, and on AMI-firmware AMD laptops the display is not
kept alive through the handoff. The *installed* system (which gets
`linux-omarchy`, a kernel that does have amdgpu) works fine — verified end
to end on this machine.

This is a hardware-class problem: any AMD APU laptop (not just this HP)
lacks a GPU driver in the live kernel.

## Environment

- Omarchy 4.0.4 ISO (`omarchy-4.0.4`), x86_64
- HP 255 G10: Ryzen 7 7730U (Mendocino, Radeon iGPU only), AMI UEFI, Secure
  Boot off, 2 TB NVMe. Panel is the only output; no dGPU.
- Comparison datapoint: a stock Ubuntu live USB boots this machine with full
  graphics (its kernel has amdgpu KMS, which re-initializes the display
  engine itself and is immune to loader console state).

## Evidence

**1. The live kernel has no amdgpu (static verification on the ISO's
vmlinuz-linux-t2, `7.2.4-arch1-Watanare-T2-3-t2`):**

- The kernel payload (PE `.text` section @ 0x5000 = 716-byte header + zstd
  stream) decompresses to a 72.8 MB vmlinux ELF.
- `amdgpu` appears exactly **2** times: `amdgpu_vm_bo_map` /
  `amdgpu_vm_bo_unmap` — generic TTM symbol names, not the driver.
- **Zero AMD PCI vendor IDs (`1002:`)** in the kernel — it cannot probe any
  AMD GPU.
- No `amdgpu/...` firmware request strings.
- Display stack present: `efifb`, `simpledrm`, `fbcon`, `drm_kms_helper` —
  i.e. framebuffer passthrough only.

**2. Kernel selection logic confirms intent, not accident**
(`/root/configurator` in the ISO's airootfs):

```bash
detect_kernel() {
  if lspci -nn 2>/dev/null | grep -q "106b:180[12]"; then
    echo "linux-t2"
  else
    echo "linux-omarchy"
  fi
}
```

`linux-t2` is selected for the *live ISO* regardless of hardware
(`arch_packages=(linux-t2 ...)` in `omarchy-iso/builder/build-iso.sh`), while
the installed system gets `linux-omarchy` (which has amdgpu — cf. the amdgpu
init logs in issue #12550 on an AMD dGPU MacBook). So AMD-APU laptops run
the Apple-targeted kernel during install and only get a working GPU driver
after installation.

**3. The live session's display is therefore 100% loader-state dependent.**
On this AMI-firmware machine, only a UEFI-shell → kernel handoff leaves a
usable GOP framebuffer; GRUB handoffs (text console *and* GOP/gfxterm) leave
the panel black. Additional firmware quirk observed: this firmware provides
no EFI FS config table, so the kernel stub cannot fetch `initrd=<file>`
(`EFI stub: ERROR: Failed to handle fs_proto` →
`Failed to load initrd: 0x8000000000000002`) — the initrd must be embedded
(UKI) for any custom boot path.

## What actually worked (full install completed)

1. Booted the ISO's `vmlinuz-linux-t2` + full initramfs as a **UKI with
   embedded initrd** from the **UEFI shell** (shell is the only handoff with
   a working display on this firmware), cmdline:
   `archisobasedir=arch archisosearchuuid=… initramfs_async=0 nomodeset`
   (`nomodeset` keeps efifb in charge — without it, the `simpledrm` KMS
   takeover blackens the panel).
2. Live session became fully visible; installed silently via the first-party
   **CIDATA autoinstall** mechanism (32 MB ISO9660 partition labeled
   `CIDATA` on the boot stick carrying `user_configuration.json` +
   `user_credentials.json`; `omarchy-cidata-load` skipped the wizard and
   `omarchy-iso-install` ran unattended from the offline mirror).
3. Reboot into the installed system: `linux-omarchy` + amdgpu drives the
   panel normally. Desktop works.

## Suggested fixes

1. **Ship a kernel with amdgpu in the x86_64 live ISO for non-Apple
   hardware** (or select `linux-omarchy` for the live kernel when no Apple
   T2 ASIC is detected, mirroring the installed-system logic in
   `detect_kernel()`). This alone would let stock GRUB/limine boots of the
   ISO show graphics on AMD APU laptops.
2. **Document a black-screen debug recipe** for AMD APU + AMI-firmware
   machines in the manual/troubleshooting: boot the ISO kernel from the UEFI
   shell as a UKI with embedded initrd + `nomodeset` (and note the
   `fs_proto` quirk that rules out `initrd=<file>` on such firmwares).
3. Optionally: note in the ISO docs that the live session on AMD hardware
   runs without a GPU driver by design (Apple-first kernel choice), so
   installer TUIs that assume KMS/gpu acceleration should be usable over
   efifb/simpledrm.

Happy to provide the full boot-stick layout and the decompilation
steps/outputs on request.