This tutorial video will show you step by step how to unlink (disconnect/remove) your Instagram account from Facebook on an Android phone in 2019.
This tutorial works for all Android phones, such as Samsung Galaxy, Sony Xperia, Google Pixel, Lenovo, Motorola, Huawei, OnePlus, Nokia, HTC, LG, and all other Android phones.
Reference: https://help.instagram.com/536741816349927