In Chrome 88, some changes were made to Largest Contentful Paint to bring its implementation in line with the updated specification, and fix bugs in the chromium implementation.
The changes are:
Each change only affects sites with specific types of content.
The change to ignore full viewport images as potential largest contentful paints will improve Largest Contentful Paint times for pages with background images. This is intended as Largest Contentful Paint attempts to time when the main content on the page is visible, and this generally is not background images.
The change to stop recording after an input in an out of process iframe will improve Largest Contentful Paint times on sites which have cross-process iframes.
The bug fix for invisible elements may result in increased Largest Contentful Paint timings for sites using a placeholder pattern that swaps in the largest contentful image.
Chrome 88 is currently scheduled to be released the week of January 19, 2021.