So you went the prefix sum route I see, this is considerably harder to get right than the counter approach.
Your best bet to debug this is to isolate each step (isolate the culling code, isolate the parallel scan, etc) and use GetData to visualize what the ouput of each stage is, making sure it is correct.
About indirect drawing in ShaderGraph, it is not supported . There’s hacky workarounds for it, but they only work somewhat reliably in DX11. It breaks in DX12 and Vulkan, and sometimes works in Metal (I speak from experience, I develop an asset for the store that uses this and it’s been a pain in the arse). Depending on what your goal is you might be fine, but I wouldn’t rely on this in a production environment. This feature is in Unity’s roadmap, but yet to be considered (vote for it if you want it!):
https://portal.productboard.com/unity/1-unity-platform-rendering-visual-effects/c/61-support-for-drawindirect-drawprocedural
Imho the lack of official support for indirect drawing in ShaderGraph plus the practical inability to hand-write shaders for HDRP means there’s no sane way to indirectly draw anything in HDRP, which is laughable considering it is supposed to be a cutting-edge, high fidelity pipeline.