Flash red focus light/Mirrorless

[D.RicPhoto]

I was watching a Youtube video by Peter Gregg. He was testing mirrorless cameras using a flash with the red focusing assist light on the flash. His conclusion was he has not found a mirrorless camera that will have the flash red focusing assist light work. I tested all the flashes I have and did not realize not one no matter the brand did the flash red focusing assist light work on the Olympus Mark series. Anyone been able to make the red light work on any mirrorless camera brand?