Not an expert, just trying to add some more context.
With time-delay cosmography[1] one exploits that unless the source is perfectly in the center of the line of sight, then the photons that make up one lensed copy have traveled a different distance from the source than photons that make up a different lensed copy. This effect can be used to measure absolute distance and give an accurate measure of the Hubble constant.
With dual source-plane lensing[2] one exploits that if two different sources lensed by the same lens, one can take the ratio of the measurements between the two sources and get results that are significantly less affected by the lens itself and is completely independent of the Hubble constant.
With time-delay cosmography[1] one exploits that unless the source is perfectly in the center of the line of sight, then the photons that make up one lensed copy have traveled a different distance from the source than photons that make up a different lensed copy. This effect can be used to measure absolute distance and give an accurate measure of the Hubble constant.
With dual source-plane lensing[2] one exploits that if two different sources lensed by the same lens, one can take the ratio of the measurements between the two sources and get results that are significantly less affected by the lens itself and is completely independent of the Hubble constant.
[1]: https://arxiv.org/abs/2210.10833
[2]: https://arxiv.org/abs/2204.03020