Nothing is said in Justin Power (2014) or Michael W. Morgan and E. Mara Green and Upendra Khanal (2016) about the external relations specifically of Afghan Sign Language (except for ASL influence). Hence, it is a presumed isolate. A systematic lexical investigation remains to be done.
Glottolog
[afg] at ISO 639-3
[afg] at OLAC
[afg] at IMTVault
Wikidata
Wikipedia