Does kubefirst support config files?

yes, here a sample of configs you can use.

Sample of AWS installation Gitlab

./values.yaml:

config:
  admin-email:  user@domain.com
  hosted-zone-name: my.domain.com
  profile: default
  bot-password: myAmazingPassword
  cluster-name: mycluster
  cloud: aws
  git-provider: gitlab

kubefirst init  -c ./values.yaml

Sample of AWS installation Github

./values.yaml:

config:
  admin-email:  user@domain.com
  hosted-zone-name: my.domain.com
  profile: default
  bot-password: myAmazingPassword
  cluster-name: mycluster
  github-owner: my_github_org
  cloud: aws

kubefirst init  -c ./values.yaml