The Steam Deck really blurs the lines between PC and console. Modern consoles use AMD64/Radeon hardware and at least the Xbox consoles use a modified Windows OS. The Steam Deck uses AMD64/Radeon hardware and a modified Linux OS. Both feature a controller-focused user interface centered around gaming.
If you exclude the Steam Deck from the definition of “console” then a console is defined by its restrictive nature and limited selection of games.
If you include the Steam Deck in the definition of “console” then a console is defined by its controller-friendly and gaming-first design (as opposed to a general purpose PC).