The Basques got the right to manage their own finances and it seems to have quelled the independence push. Financial autonomy also helped to rein in separatists in South Tirol, a German-speaking region of Italy.
Maybe the same should be extended to the Catalans.
The Basques got their most extreme terrorists put into Jail after decades of blowing up people, which you could also argue might have helped quelling their independence push as well...
Luckily I'm too young to remember, but I do know older people talking about ETA with fear and me thinking they were overblowing it, until I stumbled upon the wikipedia article with all they did and holy cow when I looked at the list of the 2000s:
Maybe the same should be extended to the Catalans.