Daylight examples :
iPhone 6 + hand lens :
https://forum.inaturalist.org/t/macro-lenses-for-smartphone-cameras/9112/45?u=sbushes
iPhone 7 + Ztylus Revolver :
https://www.inaturalist.org/observations/77517142
Low-light examples :
iPhone 7 + Ztylus, indoors with no flash:
https://www.inaturalist.org/observations/95704041
iPhone 7 + Ztylus, indoors with inbuilt flash:
https://www.inaturalist.org/observations/95840156
But it depends a lot on the phone. Newer iPhones overcome low light issues considerably but second-hand may still cost more than Ixus, so perhaps LED lighting solutions as @albertkang said better.
This is iPhone 7 + Ztylus, indoors, same subject as last but holding an LED torch on the subject:
https://www.inaturalist.org/observations/95840339
The subject on the last link has a body about 5mm long, and you have to get within a few cm to shoot it. The LED light used is an LEDlenser MT18 torch.