When users are added to the organization, is there a way I can automatically enable eDiscovery for them instead of having to enable it for each new user manually?

When users are added to the organization, is there a way I can automatically enable eDiscovery for them instead of having to enable it for each new user manually?

Yes, as an administrator, you can mark the checkbox for auto-enable for new users in the eDiscovery portal to enable eDiscovery for the new joiner automatically. This option is available under the 'Settings' tab. 

This means, every time a new user joins your organization, the new user's account will follow the same default retention policy which is enabled for the rest of the employees, excluding those for whom custom retention policy is configured.​