GrapheneOS - does allow you to root/ADB. It's just not official, just like LineageOS. You can even sign your own images and relock the bootloader and have root i f you put in the effort.

So I misunderstood about LineageOS - I haven't read anything about it for a while. Everyone on GrapheneOS's forum is really anti-root, they even mention it's not GrapheneOS anymore. From what I saw you can't get any support whatsoever if you have an issue with root or adb, which seems like a core component to any OS to me. Would've been nice if there was a community that gave each other support for rooted LOS or GOS. There could be one, though - I haven't researched it.