@DanielMcQ I ran into this issue and posted here.
https://openedx.slack.com/archives/C0GR05YC9/p1585674197001400
This SameSite cookie is effecting LTI Consumer content from rendering in an external LMSs (e.g. Canvas, Blackboard) from pulling in LTI content from our Open edX instance (LTI Provider). It throws an HTTP 403 response because the anonymous user is not authenticated because the csrftoken is not being sent in the HTTP request to https://github.com/edx/edx-platform/blob/open-release/hawthorn.master/lms/urls.py#L244-L252