[keeperofdakeys]

LineageOS no longer comes with root installed, you have to install an extra zip file while flashing to enable it - https://download.lineageos.org/extras

IIRC some root detection mechanisms still check for an unlocked bootloader.

[petecox]

And from the same web page there's an uninstall script to un-root the phone.

This is handy if you only need root occasionally, e.g. Titanium Backup, and don't mind messing about in TWRP.