As suggested on https://jfrog.com/open-source/ I pulled the "Latest Artifactory Docker Image", and it's running now, and I can access the web-GUI at port 32782, but what are the "start account" credentials?
You set the admin password while setting up in the onboarding wizard.
If you didn't use the wizard or skipped the password change, the credentials of the default Admin user are admin:password
.