I plan to write a story about a large number of space probes that are equipped with artificial intelligence and told to explore star systems and travel between them. These probes are not equipped with warp drives or any other superluminal technology. They have only one sun sail. I am looking for a material that can be used for the wiring and circuits of these probes that can withstand hundreds of thousands of years of exposure to no air and star radiation without breaking.
Fired pottery is one of the few signs we have of early humanity. Most metals corrode or naturally weld too fast to be useful in the time intervals you describe.
We've invented ceramic batteries, capacitors, semiconductors, superconductors, transistors... everything you'd need for a durable supercomputer, given some advances in fabricating the stuff.
Some ceramics have interesting optic properties too, so you might not be limited to electronic computing.