At the moment, it is not possible to manage access into Trello from a third party identity service provider via Atlassian Guard.

Suggestion : Implement user and group provisioning via Atlassian Guard with Trello

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Update as of April 24, 2023. Trello Enterprise user management and SCIM group provisioning is released to first customers. We will be gradually making this a default admin experience for all customers throughout 2023. Learn more here.

• Trello Enterprise is represented in admin.atlassian.com, alongside other Atlassian products
• Like with other Atlassian products, Org Admins are able to grant or revoke access to Trello Enterprise to users: manually, or using groups, or with SCIM IdP sync
• Trello admin dashboard is still used, as a supportive tool, for more granular administration (Trello-specific security policies, managing Trello workspaces and shadow IT)