Mezcal Negroni's absolutely rip.
I went down an amaro rabbit hole - buying a bunch of obscure shit whenever I saw something I'd never seen before.
Some worked, some didn't - the ones that didn't I drank over ice with soda. But, all in all - I found they change up the Negroni in an awesome way.
Best Alternatives to Campari I found were:
Bruto Americano
Faccia Brutto, Gorini
Distillerie Capitoline N'Amaro, hard to find
https://folkwayswines.com/
Cocchi Rosa