To be clear, I'm using Qlik Sense Enterprise February 2018 initial release. As the author of that article (@William Christensen) noted in his question at the end of that posting, the authentication options are different in this release (relative to 3.2). Below are the new authentication options:
We use Windows authentication for nearly everything at my workplace (including Qlik Sense and SharePoint sites). So, it would seem reasonable to choose 'Windows NTLM' or 'Current Windows User (NTLM)'. It turns out that option 'Current Windows User (NTLM)' is only supported for Qlik Sense Desktop. So, the best match is probably 'Windows NTLM'. I have tried supplying my Windows credentials in that option, as well as in options 'Basic' and 'Digest'. (Anonymous doesn't accept credentials.) None of them work, even when I specify my AD domain.
The author of that article did post a question himself about the lack of the Windows authentication option:
...to which he noted in his original posting that he ended up using a service account. That may be the solution in my scenario as well, but I first want to be sure that it has nothing to do with what my SharePoint admin said about REST and FBA.