T. Are there any decent pork-free substitutes for pancetta?

Depends on why you're avoiding pancetta. If you don't want pork some of the above ideas would work. If you're avoiding meat entirely, I might try some smoked paprika, Aleppo pepper or pimento d'espelette for a smoky touch and some crisped onions or shallots for crunch.

How about some smoked turkey?

I think schmaltz would work here or duck fat.