here’s an (old, Moto X4 payton) user who made AVB work by building themselves and include the key for the image - but that bar is high and you’ll need to do sign your own updates aswell: https://android.stackexchange.com/questions/233101/how-to-properly-enable-dm-verity-and-fec-for-system-on-motorola-x4-with-lineage
I speculate this will make the warning go from “yellow” use the “orange” warning screen, so will not show the animation either? can be wrong.
Anyway, I didn’t feel the heat and just got rid of the screen: [HOWTO] Moto: replace the startup screen warning