I've never rooted my phone for LineageOS (and I have installed it on at least a dozen phones now). The only thing you need to do is unlock the bootloader (which you cannot relock, like with Graphene).

A stock OS never presents root. Finding an exploit or unlocking the bootloader will allow you to install Magisk.

Lineage always presents rooted ADB in the developer options; it is "pre-rooted" for you.