I completely agree, and a strong copyleft licence is something that GPLv3 does much better than its predecessor, which is unfortunately why it has not been adopted by the Linux kernel. I foolishly assumed that GrapheneOS, given the values it professes, would be distributed under the GPLv3 licence, but I have now discovered that this is not the case, in a move that I frankly cannot understand. Hope that changes in the near future, but it’s not very likely to happen I guess

That’s the long-term plan, yeah. Moving from Linux entirely actually, as they mentioned a future microkernel project