TL;DR: This will not affect LineageOS directly. But it may affect users running the stock ROM on their device.
When the stock ROM is installed on a certified device, package installation will be gated by the package “AndroidDeveloperVerification”, which will check against the developer’s registered/verified signing identity. Google is providing an “advanced flow” opt in for power users to install unverified-developer apps after acknowledging risk and waiting a full day. This is a one-time toggle to disable verification, not something you have to redo every time you wish to install a package.
https://lineageos.org/Developer-Verification/
https://android-developers.googleblog.com/2026/03/android-developer-verification.html