Not exactly. Development of both started at about the same time, but it was a coincidence. Flang is a standard compiler, whilst LFortran is more geared towards interactive use à la Jupyter, or source-to-source compilation.

Here’s a demo of the Jupyter notebook-like interface: https://mybinder.org/v2/gl/lfortran%2Fweb%2Flfortran-binder/...