I polled my friends from Veneto and the unanimous verdict was that the only other alternative to Campari or Aperol in a Spritz is Select.

Having said that, I do love a good old Cynar - much in the same way as I like Fernet Branca. My old aunts loved a good Cynar, and while downroute in Sao Paulo I found a bottle in a bar and basically purchased it off the shelf for personal use, though a couple of my other drinking companions decided to try it and loved it. But though Fernet can be drank in a cocktail (Branca and chinotto, or coke, or the great BrancaMilano) I've always drank Cynar alone, at best on the rocks.