The solution (heavily) alluded to by GrapheneOS in https://grapheneos.social/@GrapheneOS/115164212472627210 and https://grapheneos.social/@GrapheneOS/115165250870239451 is:

1. Release binary-only updates (opt-in). 2. Let the community (a) make GPL source requests for any GPLed components and (b) let the community reverse engineer the vulnerabilities from the binary updates. 3. Publish the source once everything is public anyways.

Which just shows how utterly ridiculous all this is.