Strictly speaking this isn’t a Photonic support question as it pertains to features of third-party scripts.
To the best of my knowledge none of the lightbox scripts would pass an accessibility audit. The basis of my statement is my knowledge of the state of development of each lightbox, and a review of any accessibility-related tickets for those. Several of the lightbox scripts have had no updates for years, and several others have had open accessibility tickets for a long time. The only one where I saw some accessibility support is Magnific, and Fancybox3 has a patch available to improve accessibility, but it hasn’t made it to the core.
