To be fair even AMD has given up on the proprietary AMD driver in favour of encouraging users to use the open-source AMDGPU/Radeon drivers.
However although the fglrx/Catalyst driver is hated by Linux gamers, they will be a little miffed because the open-source driver only has OpenGL 4.1 support compared to OpenGL 4.5 in Catalyst.It also has lower performance in common gaming workloads, incomplete OpenCL compute support, and no CrossFire multi-GPU support.
AMD has promised that the new AMDGPU driver stack will have all the missing bits, but that is months away from being ready and will help those with the latest Radeon GPUs. The fglrx-free Ubuntu 16.04 is set to ship in April which will leave many high and dry for a while.