Contextual filter in path for block view display, alongside pathauto aliases in Drupal 8
So I was able to get my functionality by changing the Contextual Filter to a query parameter:



So in my widget block, I changed the link values from /press-releases/2015 to /press-releases?year=2015. Now the functionality works as wanted. Both urls /press-releases/ and /press-releases?year=all show all the press releases, and the node urls still work.