There are several options like los, calyx, arrow and other custom roms you can go with. But you would need to unlock your bootloader and root your device. Graphene is mostly for pixel devices.
Discussion
I don't believe your wording suggests the following however replying to avoid confusion for anyone that may read and misinterpret.
Flashing GrapheneOS does NOT require root, and does NOT require USB debugging.
Unlocking of the bootloader is required but so is relocking it afterwards to ensure full verified boot as GrapheneOS is a full production ready OS and not a custom ROM (misnomer).