I emailed Hunter Fujak to get the data for Canberra.
Coincidentally, the survey suggested 44% in the ACT were interested in AFL.
He stressed the sample size in Canberra wasn't big and it shouldn't be taken as gospel, but it still puts Canberra towards Perth and far above any other city north of the Barassi Line.
For comparison, 41% surveyed in the ACT has an interest in league, 30% had an interest in union and 10% in soccer. Pretty impressive to still get more league or union without any local team. Shows Canberra would likely be an easier job to get started than GWS and Gold Coast were.