

Steam for Linux is mixed 32/64, unfortunately the main executable (~/.local/share/Steam/ubuntu12_32/steam) and its associated steamclient library continues to be 32-bit only and runs with a couple of horribly dated libraries in the mix. That process does pretty much everything aside from the UI.
They’ve been flagging physical carts showing up in multiple places at the same time since the very moment the first Switch flashcart appeared (so likely before we ever had our hands on any). Places discussing the flashcart had been talking about increased detection and bans for a year or so.
It was even done on the 3DS before that. The 3DS had a whole tiny niche ecosystem of people selling “private headers”, dumping only the unique per cartridge info and selling it with the promise that they’d only sell any given header to one person. That too had a few instances of normal people complaining about bans with pre-owned games.