When you google “the flag of Ahmad Shah Durrani”, this black triangular flag pops up. It is fake.
Iranica Encyclopaedia says:
“Almost nothing is known about the flags of Afghanistan during the reign of the Sadōzay dynasty and the early decades of the Moḥammadzay dynasty. Traditionally, nonstandard flags of different colors were used in wars. In the reign of Amir Dōst Moḥammad (1819-63) and Šēr ʿAlī Khan there existed triangular, red and green military flags bearing the words of the Islamic confession of faith (šahāda) as well as the name of the four caliphs and verses from the Koran relating to jehād “holy war,” all in white color”. The earliest Afghan flag shown in vexillological books of the 19th century has green-white-green horizontal stripes.”In the reign of Amir ʿAbd-al-Raḥmān Khan (r. 1880-1901), black became the standard color of the royal/national flag. Contemporary stamps and coins reveal the formation of a modern coat of arms which became a persistent symbol on the national flags for coming decades: a temple/mosque flanked by two flags, inside of which are a meḥrāb (prayer niche) and menbar (pulpit). The arms were surrounded by muskets, sabres, cannon, and it appears in white on the black flag (“Bayraq”).
Read the full article about flags of Afghanistan here
The tree like structure in the fake flag is straight from the Lord of the Rings movies (thanks to Saddam Yousafzai in the comments for pointing it out)