OmniROM was a popular custom ROM back in the Jelly Bean/KitKat era, especially because of its multi-window feature and wide device support. The project has scaled back its reach over the years, like most custom ROMs (except LineageOS), but it still maintains a dedicated user base.
OmniROM has started to offer official Android 8.1 weekly builds, beating LineageOS to the punch. Oreo is currently available for the OnePlus 3/3T, OnePlus 5, and Samsung Galaxy Tab S2.
OmniROM begins weekly Oreo 8.1 builds was written by the awesome team at Android Police.