Assign Tasks to Anyone

What I've found so far, but don't have the privilege to see if it's all accurate or not (can't provide links because this interface doesn't allow it, also had to remove bullets):

Make sure your admin goes to Microsoft 365 Groups settings and turns on guest access to group content. This will ensure that guests can access projects shared with them in the group, and that they can be added to your Microsoft 365 Groups through Project. You'll be able to search for them in the Group Members dialog, and when you assign a task.

Project builds on the Microsoft 365 Groups guest access feature.

A project owner can add a guest who is part of the organization to the project group by selecting Group Members at the top of their project and searching for the person's name. Another way is to select a task, selecting the assign icon, and then searching for them. 

 It will only work if a Group Administrator turns on the access setting Let guest group members access group content.

Note that for projects in custom environments, guest users with Microsoft 365 licenses or no licenses can view but not edit projects. Guest users with Microsoft 365 E3 and E5 licenses can update the completion percentage of tasks assigned to them.

...Can a guest edit project content? 

Yes. Any guest can edit the content of any project that is shared with them. 

Can I keep track of guest assignments WITHOUT giving them access to the project?

Yes, you can use the “Just assign” option after assigning a task to a guest to simply keep track of the task assignment without sharing sensitive information with the guest. 

Can a guest access the groups documents and SharePoint sites attached to project tasks?

Yes, if the organization has enabled the appropriate settings for guest collaboration in SharePoint. 

Can a guest access the project through Teams?

Yes, a guest can view your project in Teams if the project is pinned to your team’s channel.