So yes it's likely ADFS is the culprit here. I haven't done extensive development of this connector as shortly after releasing it Tableau released their native Sharepoint connector which I'd recommend you use instead.
Yes, that is where I started; trying to use the SharePoint List connector. I tried several permutations of trying to use it, but it throws errors such as this.
I tried Integration Authentication and Username and Password. Neither one seems to work. Our SharePoint Administrator says I have full access and he even tried to setup a connector as Administrator and he gets the same errors I do.
If the issues is ADFS do you know of a workaround?
I have limited knowledge/experience in getting this to work, but can tell you that we have multiple SharePoint servers and I can only connect to some of them. From what I can tell, there is some network shenanigans going on with some of the SharePoint servers that are exposed externally to outside organizations. I believe they may be in our DMZ or have "unique" network routing paths for authentication.
If a possibility I would try connecting to other SharePoint servers you have access to.