Is there a serious textual variant that I am unaware of that would make the NA28 not include Acts 15:36-41?
It seems to depend on which NA28 resource you are using - I don't know why
Very odd.
That pericope has dropped out of Nestle-Aland Greek New Testament, 28th Edition (resource id LLS:NA28 2017-07-07T17:02:11Z).
However, it is intact in Nestle-Aland: Novum Testamentum Graece, 28th Auflage (resource id LLS:NA28GBS 2017-05-08T18:26:08Z).
A cut-and-paste scribal error?
Very odd. I'll look into it.