Well, two layer anyway. People have printed overlapping traces into 3d printed volumes before, but it's a very flawed process. High currents are basically out

Well, two layer anyway. People have printed overlapping traces into 3d printed volumes before, but it's a very flawed process. High currents are basically out of the question (resistance too high), analog voltages are very hard (inconsistent resistance), complex circuits struggle with connecting traces, and high speed circuits struggle with grounding/shielding. It's possible to achieve shockingly good results by electroplating (https://youtu.be/Tx2B5hI4w1U https://youtu.be/Tx2B5hI4w1U) but there are heavy caveats. There isn't really a process that approaches pcbs in a single area, much less all of them. Unfortunately that's more limiting than you'd expect- even very cheap ARM processors will probably be unstable without a ground plane and low resistance traces. I hear there's some interesting stuff coming in 2021 (can't tie rumors to my real name) and lots of people are working on this kind of thing, but the solutions are non-obvious. SLA is having a lot of trouble because it's hard to include a lot of conductive powder without degrading resin quality (and worse, it blocks the light), sintered stuff struggles with mixed powders, and resin stuff struggles with density and continuous lines/planes.