Fwiw there's a really nice write-up on how Steam Deck does A/B updates, using rayc and casync/desync. https://github.com/randombk/steamos-teardown/blob/master/doc...

Also Collabora had a nice update on tuning work they did. https://www.collabora.com/news-and-blog/news-and-events/stea...

I'm a little surprised they use casync and multiple partitions, given that root is on btrfs. As they have it is more reliable if anything does go bad, so makes sense, but: given that steam decks are on a given snapshot of the btrfs system, it seems like they could just send an incremental update to the next release and try to boot that. Oh ah, that breaks down if, like me, you disable the readonly root.