Libre Hardware

Depending on the GPU model, it is possible to use an AMD GPU without installing non-free drivers or firmware, though the designs are not actually copyleft and so not fully libre in this sense. Every AMD CPU since 2013 comes with the Platform Security Processor (PSP) which is a hardware backdoor, so choosing a modern AMD CPU is ill-advised regardless of whether you want a fully libre hardware configuration.

On the CPU side, the most libre options are probably RISC-V CPUs. I don't know if the Sophon SG2042 is fully free, but that might be one example. (Note, however, that its Xuantie C920 cores are vulnerable to GhostWrite.) On the dedicated GPU side, I'm less familiar with the options. You'd be more likely to find a libre system-on-a-chip (SoC) that pairs RISC-V CPU cores with some sort of integrated GPU. Someone else might be able to provide real-world examples. (I'm not looking to invest in new hardware any time soon, so I haven't researched the latest and greatest.)