I'll supplement the answer of @beeshyams: since Android O is still in Dev Preview phase, the source code is still incomplete, and no custom ROM (LineageOS, etc.) could even base their work off it. LineageOS (back in their CyanogenMod days) also stated time and again that they will not touch Dev Preview code.
To reinforce the fact: until Android O is officially released (name confirmed and source code out), there's no way you can taste it on an unsupported device.
P.S. Historically, there had been ports of Android L and M Dev Previews to other devices, based on the image released alone. However, 1) such ports are often conducted between devices of similar SoCs, 2) those ports are nowhere near stable and usable, and 3) they quickly become obsolete once the proper release source code arrives.