> Based on the fact that many ROCm packages exist in guix, and
> that I don't see people complain, it seems it must have worked in the
> past.
Indeed, I am using Guix’ darktable and rocm-opencl-runtime packages
for OpenCL-accelerated photo editing. But I’m also doing this on a
foreign distribution with a custom kernel (5.15) – not Guix System.

> > ROCk module is loaded
> > Unable to open /dev/kfd read-write: No such file or directory
> > <my username here> is member of video group
Which GPU are you using? Can you see it with `lspci` and does it have the
`amdgpu` driver attached? Is the firmware loaded (`dmesg | grep amdgpu`,
I’m guessing no, since you use linux-libre)?

I have an AMD Radeon Instinct MI60, one of the few officially supported GPUs.  `lspci | grep -i amd` gives:
01:00.0 PCI bridge: Advanced Micro Devices, Inc. [AMD/ATI] Device 14a0
02:00.0 PCI bridge: Advanced Micro Devices, Inc. [AMD/ATI] Device 14a1
03:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] Vega 20

so it seems to be detected. `dmesg | grep amdgpu` gives:
[   12.446826] [drm] amdgpu kernel modesetting enabled.
[   12.485012] amdgpu 0000:03:00.0: amdgpu: Trusted Memory Zone (TMZ) feature not supported
[   12.522503] amdgpu 0000:03:00.0: amdgpu: Fetched VBIOS from ROM BAR
[   12.522538] amdgpu: ATOM BIOS: 113-D1630600-107
[   12.523127] [drm:sdma_v4_0_early_init.cold [amdgpu]] *ERROR* sdma_v4_0: Failed to load firmware "/*(DEBLOBBED)*/"
[   12.523277] [drm:sdma_v4_0_early_init.cold [amdgpu]] *ERROR* Failed to load sdma firmware!
[   12.533887] amdgpu 0000:03:00.0: amdgpu: MEM ECC is active.
[   12.533889] amdgpu 0000:03:00.0: amdgpu: SRAM ECC is active.
[   12.533893] amdgpu 0000:03:00.0: amdgpu: RAS INFO: ras initialized successfully, hardware ability[7fff] ras_mask[7fff]
[   12.533902] amdgpu 0000:03:00.0: amdgpu: VRAM: 32752M 0x0000008000000000 - 0x00000087FEFFFFFF (32752M used)
[   12.533904] amdgpu 0000:03:00.0: amdgpu: GART: 512M 0x0000000000000000 - 0x000000001FFFFFFF
[   12.533905] amdgpu 0000:03:00.0: amdgpu: AGP: 267878400M 0x0000008800000000 - 0x0000FFFFFFFFFFFF
[   12.557543] [drm] amdgpu: 32752M of VRAM memory ready
[   12.557549] [drm] amdgpu: 24018M of GTT memory ready.
[   12.557775] amdgpu 0000:03:00.0: amdgpu: failed to init sos firmware
[   12.557777] [drm:psp_sw_init [amdgpu]] *ERROR* Failed to load psp firmware!
[   12.557916] [drm:amdgpu_device_init.cold [amdgpu]] *ERROR* sw_init of IP block <psp> failed -2
[   12.558042] amdgpu 0000:03:00.0: amdgpu: amdgpu_device_ip_init failed
[   12.558044] amdgpu 0000:03:00.0: amdgpu: Fatal error during GPU init
[   12.558047] amdgpu 0000:03:00.0: amdgpu: amdgpu: finishing device.
[   12.602981] amdgpu: probe of 0000:03:00.0 failed with error -2
[   12.603026] [drm] amdgpu: ttm finalized