Currently, Microsoft Teams does not have a built-in feature that allows you to automatically share a Loop component link with new members in the same way that pinned comments work in Discord. However, you can manually share the Loop link in the Teams chat or channel where your team collaborates. This way, whenever new members join, they can access the link you provided in the chat history.
To streamline the process, you might consider creating a standard message or a pinned message (if your organization allows it) that includes the Loop link, so new members can easily find it when they join the conversation.
Additionally, if Loop components are enabled in your organization, you can create and share interactive Loop components directly within Teams messages, allowing all members to view and collaborate on the checklist in real time.
For more details on how Loop components work in Teams, you can refer to the documentation on Loop components in the Microsoft 365 ecosystem.