I installed vanilla forum locally to test, and I don't have Import option to import data from another forum.
Cloned from github and build with phing.
Did I miss something?
What you have missed is that the current official version is 2.6.4, downloadable from this site. What you have used is a development version and you shouldn't use that.
Try it with 2.6.4 and see if that is working for you
Thank you, all is good now!