What is the best alternative to Light Meter LM-3000 on iPhone?

Photone - Grow Light Meter, S tier, #1 in light metering.

Is there a free alternative to Light Meter LM-3000?

Yes: Photone - Grow Light Meter (S tier, #1) is free to download, with in-app purchases.

Yes. 1 app ranks above it in light metering: Photone - Grow Light Meter (#1).

Light Meter LM-3000 is A tier, #2 of the 6 tiered apps in light metering. Here is everything that competes with it on iPhone, in tier order.

1
Photone - Grow Light MeterShigher tier
Free + IAP · ★ 4.6 · 7,242 ratings · score 93
Turns an iPhone or iPad into a PAR meter that measures plant light as PPFD, DLI, lux, foot-candles and color.
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 Light Meter LM-3000 on iPhone?: Photone - Grow Light Meter, S tier, #1 in light metering.
Is there a free alternative to Light Meter LM-3000?: Yes: Photone - Grow Light Meter (S tier, #1) is free to download, with in-app purchases.
Does anything rank above Light Meter LM-3000?: Yes. 1 app ranks above it in light metering: Photone - Grow Light Meter (#1).