https://gpuopen.com/ags-sdk-5-4-improves-handling-video-memo...
Which says:
"For APUs, this distinction is important as all memory is shared memory, with an OS typically budgeting half of the remaining total memory for graphics after the operating system fulfils its functional needs. As a result, the traditional queries to Dedicated Video Memory in these platforms will only return the dedicated carveout – and often represent a fraction of what is actually available for graphics. Most of the available graphics budget will actually come in the form of shared memory which is carefully OS-managed for performance."
The implication seems to be that you can have an arbitrary amount of graphics RAM, which would be appealing for AI use cases, even though the GPU itself is relatively underpowered.
Still, the question remains open, how to precisely control APU/GPU memory allocation on Linux and what is the limitations?