Is there any persistent root method for LineageOS 20?

The gist of it is that I use LineageOS for the Samsung S9 and I use Magisk. Every time the system updates the root is removed, so my question is - does anyone know of any persistent way to get a persistent root? Apparently AddonSU.zip has been dropped and from my surface research, the answers are very underwhelming. I mean re-adding Magisk is not the end of the world but I really would like it if it were to get stuck around every time the OS updates... BTW, I would like the long answer of why it happens. I have the vaguest idea that every update overwrites the boot partition or image where Magisk injects itself during boot. But I would like a somewhat in-depth explanation of how Magisk does its thing and why the updates screw it up.