I have an open ticket with the support about this.
No updates.
For windows they suggest going to configuration, group and downloading the custom installer, no such option for linux distros.
Same issue.
Old free account 4/5 systems, group definitely exists
1 organization found. Please select the organization
[1] xxx
Enter selection: 1
1 site found. Please select the site
[1] xxxx
Enter selection: 1
No agent groups available. Please create a agent group for the selected site.