What is the best alternative to Photone - Grow Light Meter on iPhone?

Light Meter LM-3000, A tier, #2 in light metering.

Is there a free alternative to Photone - Grow Light Meter?

Yes: Light Meter LM-3000 (A tier, #2) is free to download, with in-app purchases.

No. Photone - Grow Light Meter is #1 in light metering.

Photone - Grow Light Meter is S tier, #1 of the 6 tiered apps in light metering. Here is everything that competes with it on iPhone, in tier order.

2
Light Meter LM-3000A
Free + IAP · ★ 4.5 · 4,584 ratings · score 89
Measures illuminance (lux or foot-candles) and correlated color temperature (Kelvin) using the iPhone's front-facing.
3
Photo Light & Exposure MeterA
Free + IAP · ★ 4.5 · 4,437 ratings · score 89
Light meter that suggests exposure settings in real time and measures shutter speed, lux, EV and color temperature.
4
Lux Light Meter ProB
Free + IAP · ★ 3.9 · 8,341 ratings · score 72
Measures light intensity in lux and foot candles, with exposure settings for photography and lighting checks.
5
myLightMeter PROC
$4.99 · ★ 4.8 · 2,864 ratings · score 67
Exposure light meter for film and digital photography with manual controls, metering modes, and session logging.
6
Lightme - LightmeterC
Free + IAP · ★ 4.8 · 951 ratings · score 67
Lightmeter app showing multiple aperture and shutter combinations, with spot, continuous and pinhole metering modes.

What is the best alternative to Photone - Grow Light Meter on iPhone?: Light Meter LM-3000, A tier, #2 in light metering.
Is there a free alternative to Photone - Grow Light Meter?: Yes: Light Meter LM-3000 (A tier, #2) is free to download, with in-app purchases.
Does anything rank above Photone - Grow Light Meter?: No. Photone - Grow Light Meter is #1 in light metering.