I'm not sure of the official source, but I know that in Legends it was established that, in some way, Han saved Chewie and Chewie, owed him a life debt, which is why he followed Han through the galaxy.
In the film Solo, we are given a new canon version of their first meeting, where Han helps Chewie and him both escape from the Empire and go on the run. However, this bond between them is never called a life debt in the film, and Chewie doesn't even stay with Han throughout the whole movie. When Chewie goes off to free his fellow wookiees, he later makes the decision to return to Han.
However, in the Disney canon novel Aftermath: Life Debt (aptly named) Han references that Chewie owes him a life debt from some past event.
So — what is this event? What happened in their past that made Chewie indebted to Han? I'm looking for Disney Canon answers, not Legends.