Nothing, HIP is essentially API compatible. That gets you nothing because CUDA nVidia optimized code will perform quite abysmally on a Radeon/Instinct.

And furthermore nVidia has a bunch of proprietary libraries AMD has not cloned either.

Normal people use Tensorflow, Keras or PyTorch anyway, not raw CUDA or even its libraries. The one place that is the stronghold of raw CUDA is molecular dynamics simulations because it's been written ages ago by some researcher who has never heard of Tensorflow etc. And probably uses cublas and/or cufft for which the AMD replacement is a joke and incompatible API. Situation there is slowly improving finally with Magma.