> what does someone running Linux do if the government mandates online services require proprietary attestation APIs?

One dual-boots to a reputable Linux vendor’s signed/sealed OS image with secure boot enabled in BIOS, so that the attestations are valid; financially supports said vendor; contacts them quarterly with check-ins on the status of their lockdown+attestation roadmap and uses professional journalism approaches to highlight their (in/)action; and, contacts one’s relevant governing body to petition for the addition of that vendor’s signed/sealed product line to be added to the authorized signatures list by both government-sponsored apps and to the verification platforms of the competing vendors (in order to balance the necessities of attestations with an appropriate degree of anti-monopolistic protections for consumers).

> It's scary how quickly the banning is moving. The problem is what happens next. When they realise that banning things doesn't really work

This confidence that ‘attestation doesn’t really work’ is the same sort of confidence that lead the Linux user community to largely scoff at, and ignore, attestation’s threat from when it was ballistically launched three decades ago towards the future. Options are now very limited for stopping it, and largely reduced to ‘getting some Linux into the approval list’. Severe compromises in user freedom will be required for the signed+sealed distro images to receive government approvals.

Imagine if Linux were an app on a video game console and you start to see the outcome: it’s a perfectly great working environment into which all of /usr/local and /opt and /home are writable, but the lockdown prevents you from modifying the OS in any way that could defeat the attestation protections. Apps you install into /opt can only access their own /opt/prefix, apps you install into /usr/local can access $HOME. The apps you install can choose to write session data (such as digital age verification certificates) to a system-protected /data store keyed first by the kernel’s signature, and second by the vendor signature the kernel reads from the app; with the understanding that an attestation latch-forward after an exploit patch will wipe that store, and that dual-booting to a different vendor will suspend access to sessions stored by that vendor.

This is, to climb on my hobby horse for a moment, why I continue to believe that Valve will be the first Linux vendor to receive government attestation approval alongside Apple / Google / Microsoft have previously across the desktop and mobile spaces. I’d really prefer that to be Graphene, Ubuntu, and Valve — but Graphene’s customer base is hostile to this, Ubuntu doesn’t have any incentive to care, and of the Linux vendors out there, Valve has a decade-long head start on the need for a locked-down and attested platform for business reasons. All of the above falls out naturally from considering how to defend one app from another on Android, iOS, Steam Deck, and Xbox. So far as I can tell today, though, Linux intends to be left out in the cold on all this. Oh well.