Over a year ago the AMD APU support in the Radeon Open eCosystem (ROCm) stack was quietly removed and has yet to be re-enabled in the upstream ROCm packages. But should you be wanting to use ROCm for their compute APIs or OpenCL on APUs, unofficial Ubuntu packages are now available to provide this capability.

Engineering firm Bruhnpace AB has resorted to providing their own ROCm packages for Ubuntu 18.04 with AMD APU support enabled to make up for AMD's lack of official packages handling APUs in the different ROCm libraries. The repository doesn't provide its own rocm-dkms package but rather recommends users run the latest upstream kernels for the AMDKFD kernel driver support.

Long story short, if you are running an AMD APU like Carrizo or Raven Ridge / Picasso and want ROCm compute support on Ubuntu, see here for instructions on these unofficial/experimental packages. Hopefully upstream ROCm packages will return to enabling APU support in the future.