The Zendesk Suite Team & Growth licence packages don’t include access to side conversations.
Side conversations allow agents to have multiple separate discussions with different people outside of the platform, all while keeping references to the ticket. Recipients can only see the conversations they are part of and won't have access to the original ticket thread.
The Zendesk Support Linked Ticket app allows you to create a child ticket from an existing parent ticket and connect the two. This feature is especially handy when you need to manage two separate discussions about the same issue.
For instance, if a customer contacts you regarding a problem and you need to involve a third party to help resolve it, the Linked Ticket app enables you to create a child ticket from the original customer ticket. This keeps the third party's access limited, ensuring they don't see your customer's details, while still linking both tickets in the agent's view.
The linked ticket app will only let you have a single separate conversation using a child ticket. It’s not a full replacement for side conversations, which allow for multiple separate discussions. However, it does offer an alternative conversation feature within the Suite Team and Growth plans.
Please have a look at this Zendesk article, here regarding the installation and use of the Linked Ticket App. You might find the section on creating a child ticket from a parent ticket particularly helpful.
Note, the Linked Ticket App has already been installed for you as part of your OnRamp solution.