Think your title is a bit misleading. A flagship phone is a flagship of that brand generally. There's lower end Samsung and Apple still sell the 5S.
Personally I'm using an LG G6, i like the design and performance is good for the money. It would probably be considered a flagship phone though, or at least was until the V30 came out.
Non-flagship phones that we sell a lot at company are the Lenovo/Motorola Moto G series, Samsung J5 series and Huawei Honor 8.