I just saw this presentation at the Chaos Computer Club conference, for an “Ethical Hardware Kit with a PCB microcontroller made of wild clay retrieved from the forest in Austria and fired on a bonfire. Our conductive tracks use urban-mined silver and all components are re-used from old electronic devices”. It was part of the feminist hardware strand!
Ceramics arent unheard of in terms of pcbs and ic packaging, though forest clay certainly isnt the ideal ceramic by any means. Ceramics also are much harder to work with and create things like vias. They are sometimes used in interposers or for creating interconnects in chiplet designs due to their capacity for high density microvias