At the moment, dx
supports these container registries:
Don’t see your container registry? Check out my Roadmap
Similar with GKE authorization, to authenticate Diginext with GCR, you need a Gcloud Service Account, if you already got one, you only need to access Google Cloud Console and assign GCR read & write permissions to it, then get back to your workspace and fulfill the form.
DigitalOcean provides API access token to authenticate with their Container Registry