>The same reason that stopped everyone else that tried, the mobile os market is mature and not enough people want or care about another mobile os to make it worth the effort.

The point is that they have one now. SteamOS is 10 years old at this point. They've undoubtedly dumped millions into it already, and done most of the wireless networking, battery performance, and UI work needed for Steam Deck. It's a pretty short leap for a company like Valve to add a 5G modem and miniaturize the form factor from there.

I've no doubt they can make it technically speaking. It's just not enough people would buy it to make it worth their while.

Exactly. iOS and Android are good enough for most people. The number of people who'd buy a 'real' Linux-based smartphone simply on principle is tiny.

How many would buy a gaming-first phone (by Valve)? I don't quite know what such a product would mean in practice, or if there is a killer "app" (game) for phone. But it would have higher probabilities of success than "a real Linux phone".

Gaming oriented phones exist for sure. One by Valve with SteamOS, yeah maybe.

It's hard to get around the awkwardness of the physical button problem though: having buttons makes the phone awkward, not having them makes gaming awkward.