If you use Apple Photos or Adobe Lightroom to annotate your faces, Peakto will read them.

You are able to filter on faces using the filter panel:

And in the faces cluster view, it's possible to get the annotation back in Peakto own faces quicly in the "Person annotated in other software".

If you tag images from another software, it sometimes write some information in the associated xmp file. 

Adobe Bridge, Photo Supreme use the standard IPTC-Extended field named "person in image" and Peakto is able to read-it.

Peakto can't transform it in a complete face annotation (we don't have any information about the face location).

Anyway, it's possible to search on this field. Enter the name of the person in the search field (1), choose metadata tabs and then click on "search all" (2)

Then you can filter on all images annotated in the other software.