Q: When faceting by model, how can I stop fabletools::autoplot() from using the color aesthetic for models?

This is related to the question Facet a fabletools autoplot of a fable forecast by model. There was a great hack proposed in the comments. I replicate it below. But I don’t imagine this is what the authors of fable intended. What’s the non-hack approach?

I’m kind of struggling to understand how fabletools::autoplot() thinks about plotting, even after going through documentation and a debugging session. I think an answer to my specific question above will end up resolving some of my general struggles in understanding.

library(tidyverse)
library(tsibble)
library(feasts)
library(fable)
library(fabletools)

tourism_melb <- tourism %>%
  filter(Region == "Melbourne") %>% 
  filter(Purpose == "Business") %>% 
  select(-Region, -State, -Purpose)

fableModels <- tourism_melb %>% 
  model(arima = ARIMA(), tslm = TSLM(Trips ~ trend()), mean = MEAN(window = 4))

forecasts <- fableModels %>% 
  forecast(h = "2 years")

forecasts %>% autoplot(tourism_melb) + facet_wrap(~.model, ncol = 1) +
# the great hack
scale_fill_manual(values = rep(NA, 3), aesthetics = c("color", "fill"), guide = "none")