Hi @sambapete, I am also looking into this. I have a Provider configured on a Nutmeg platfrom and I am able to display content from it in another Open edX platfrom (Maple) via the Consumer XBlock and in saLTIre: LTI Platform emulator but only with the anonymous authentication.
I created the Consumer credentials on the Provider platform at: /admin/lti_provider/lticonsumer; the URL I am using is https://{host}/lti_provider/courses/{course_id}/{usage_id}, and I am not doing anything special with the content on the Provider platform, I added some HTML blocks to a course and got the usage_id’s as I explained here: 12.6.3. Determining Content Addresses — Building and Running an Open edX Course documentation
I have no experience with the “old lti module” you mentioned in Slack, how did authentication work there? I am trying to figure out the TPA authentication as I commented on this post.