I always thought that Purism had no dedicated GPUs because of some freedom issues but now when I know that AMD has great open source drivers I’m really curious to know what’s the thing that made Purism take that decision? Are there some other firmwares that are not FOSS and are required to be run in order to use the dedicated graphics card? Or perhaps there’s something else to the story that I’m missing…
Thanks
If that’s the case, then it shouldn’t be too hard to run an external GPU via USB-C.
Sure, one could do that but then it’d become a sort of a semi-desktop machine 
Even a modern AMD Vega APU would be quite powerful without having to resort to a dGPU (in fact I’d prefer this approach for cash/power saving and simplicity).
Yes, there is the need of closed source firmware for 3D acceleration. 2D performance is fine but anything intensive would just fall apart (like trying to render something or playing supertuxkart etc).