I confirm FK doesn't work on stock 8.1 (stable), though it works with stock 8.1 beta (jun security patch). Void works on stock 8.1 (stable), but it's not that effective. So are Mint, Moun and Meta (all of them are based on Void). So, for now, it's best to stick to stock kernel until @flex1911
optimize their kernels for 8.1 (stock).