or by having Privileged Extension (for background installs & auto-upgrading) and a personal repo (for batch installs)
edit: typo
You _can_ install it with Magisk (which also provides root) but it can also be flashed as a regular flashable ZIP (which just requires an unlocked device).
Last (and best) of all, it can be added to an unrooted ROM. RattlesnakeOS[0] for example includes it.