The Intel Beignet driver (old OpenCL support, which was buggy and discontinued) was added to a list, the Intel NEO driver (new as-of-years-ago OpenCL support) has not been (AFAIK). It works well with darktable, at least on my laptop.
I’ve been using the NEO one for a while now with darktable and it does speed things up, even on my older laptop with Intel HD Graphics 620 on Kaby Lake (XPS 13 9360, late 2016).
I’d suggest running darktable-cltest and see what happens.
For reference, here’s the output of both clinfo and darktable-cltest on my system:
clinfo.txt (12.5 KB) darktable-cltest.txt (43.6 KB)
The official page for Intel NEO OpenCL is @ GitHub - intel/compute-runtime: Intel® Graphics Compute Runtime for oneAPI Level Zero and OpenCL™ Driver
Note: At least on Fedora, I need to install packages that Intel has built in a Copr. It’s not included in Fedora by default. The official Intel Compute Runtime project has information on how to install it other distros (and Fedora too):