I don't believe Google is sponsoring any more free shuttles. Your best bet nowadays is ponying up $10k to get a tiny chip on sky130 (so small you really can't hold even mildly complex in-order RISC-V cores). Sky130 is also generally so old that you can probably get better performance (let alone area) on a modern FPGA for a fraction of the price. Efabless's sky130 MPW is nice for semiconductor research insofar as it makes it more realistic to actually fab designs but it's not particularly useful for hobbyists beyond just the novelty of holding a chip you designed in your hands.