Settings -> Devices & connections -> Controllers & headsets -> (Select your controller) -> (Three dot menu) -> Update now.
(Blanked out the reflection of my garden)
Settings -> Devices & connections -> Controllers & headsets -> (Select your controller) -> (Three dot menu) -> Update now.
(Blanked out the reflection of my garden)
IIRC there are firmware updates for older Steam controllers that are also required to work in certain cases with Steam Decks.