With Mesa 23.1 and rucsticl I just get a black image in darktable …
[opencl_init] opencl library 'libOpenCL.so.1' found on your system and loaded [3/253]
[opencl_init] found 1 platform
[opencl_init] found 1 device
[dt_opencl_device_init]
DEVICE: 0: 'AMD Radeon RX 6900 XT (navi21, LLVM 16.0.5, DRM 3.52, 6.3.7-1-default)'
PLATFORM NAME & VENDOR: rusticl, Mesa/X.org
CANONICAL NAME: rusticlamdradeonrx6900xt
DRIVER VERSION: 23.1.2
DEVICE VERSION: OpenCL 3.0
DEVICE_TYPE: GPU
GLOBAL MEM SIZE: 16384 MB
MAX MEM ALLOC: 2048 MB
MAX IMAGE SIZE: 16384 x 16384
MAX WORK GROUP SIZE: 1024
MAX WORK ITEM DIMENSIONS: 3
MAX WORK ITEM SIZES: [ 1024 1024 1024 ]
ASYNC PIXELPIPE: NO
PINNED MEMORY TRANSFER: NO
MEMORY TUNING: NO
FORCED HEADROOM: 400
AVOID ATOMICS: NO
MICRO NAP: 250
ROUNDUP WIDTH: 16
ROUNDUP HEIGHT: 16
CHECK EVENT HANDLES: 128
PERFORMANCE: 0.188
TILING ADVANTAGE: 0.000
DEFAULT DEVICE: NO
KERNEL BUILD DIRECTORY: /usr/share/darktable/kernels
KERNEL DIRECTORY: /home/asn/.cache/darktable/cached_v1_kernels_for_rusticlAMDRadeonRX6900XT_2312
CL COMPILER OPTION: -cl-fast-relaxed-math
KERNEL LOADING TIME: 0.4416 sec
[opencl_init] OpenCL successfully initialized. Internal numbers and names of available devices:
[opencl_init] 0 'rusticl AMD Radeon RX 6900 XT'
[opencl_init] FINALLY: opencl is AVAILABLE and ENABLED.