In case of "lowest" house edge then I can say that 999dice has the lowest one because their HE is 0.1% but I would not recommend you to put your money on that site because there are many scam accusations against 999dice.
There were also some moneypot apps that has variable house edge starting from 0.1% as well but I'm not really sure if the apps are still alive or not.
Well it should be common sense then. They have a crazy low house edge and how do they stay in business? They must be scamming people.
Unless the site got tons of traffic like PD they can't afford such a low house edge.
Usually there are promos and they have 0% house edge for like a day or week or so. Those are usually legit but they are temporarily.