Arrow vendors https://github.com/mpark/variant. The vendored version is from 2019, which has issues compiling with NVCC (CUDA compiler). Projects like cuDF that depend on Arrow are stuck on a version of Arrow from before this dependency was added because they can't compile.
mpark/variant's two most recent PRs are fixes for NVCC compilation.
We would like to move cuDF forward to Arrow 0.16 or 0.17 soon, so it would be great to update the version mpark/variant in Arrow.