Good day.
Is there any way to generate gcd-token without accessing duplicacy.com/gcd_start? Say, the same way you setup rclone and google drive…
If this site goes offline for whatever reason, or the company goes in flames so to speak 
then this address won’t be reached obviously.
Thank you.
Tokens generated that way rely on duplicacy.com being up all the time to facilitate periodic token renewals.
Rclone accomplished this by running local web server for the duration of renewal instead.
Duplicacy uses external web app hosted on duplicacy.com (the exact URL you can lookup in the gcd_token you’ve downloaded)
To avoid dependency on that webservice you can use google service account with impersonation (rclone also supports that btw).
Here is how: Duplicacy backup to Google Drive with Service Account | Trinkets, Odds, and Ends
Do I really need a global service account?
Can’t I just make oauth tokens and a project for a specific user?
I don’t think you can.
You can however share the folder from your user account with the service account and not enable domain delegation for the latter. (Backing up to the shared folder was broken in duplicacy for some time)