So far it’s just a warning from Steam that it will happen on the 1st of January 2024, and it’s definitelly not an issue with Windows: Valve is chosing that the Steam launcher will not be supported in a specific Windows version anymore, and because most games bought via Steam check with Steam on startup in order to start - even when that’s not at all required by the game itself - it might mean (depending of how they do it) that games will simply refuse to start even though the game itself was and still is 100% compatible with that version of Windows.
That’s definitely a Windows issue and not a Steam issue.
So far it’s just a warning from Steam that it will happen on the 1st of January 2024, and it’s definitelly not an issue with Windows: Valve is chosing that the Steam launcher will not be supported in a specific Windows version anymore, and because most games bought via Steam check with Steam on startup in order to start - even when that’s not at all required by the game itself - it might mean (depending of how they do it) that games will simply refuse to start even though the game itself was and still is 100% compatible with that version of Windows.