It's just so logically contrived (and if the only thing left working were offline features, the conclusions may have been different) but just switching to the csgo_legacy branch in cs2 seems pretty straightforward really.
Topic on Talk:Counter-Strike: Global Offensive
I am not sure what point you're making? The availability row for Steam still details the "csgo_legacy" branch. The row is otherwise marked as "unavailable" since CS:GO has technically been "unlisted" and made unavailable except as a legacy branch through CS2.