https://github.com/radxa/kernel/tree/linux-6.1-stan-rkr4.1 , commit 8c5a7e2ee229007f8f430df4c463cd755c017e9f , but then I applied quite a few patches to make it work for Pi S and the USB audio gadget, maybe some of them are already in the newer commits. E.g. Rock Pi S + radxa kernel linux-6.1-stan-rkr1 - inactive USB host? - see the last post, it was never fixed by Radxa.
It would definitely be good to have a properly working relatively recent Pi-S kernel 