There are all kinds of copybooks on the market, so you can choose and practice whoever you like.
Recommended: Tian Yingzhang, Si Mayan, Gu Zhongan, Li Hongchuan. Their level of hard pen calligraphy is universally recognized, and there is not much controversy. Moreover, they do not publicize their personal style, and practitioners have a lot of room to play.
Oh, yes, I remember. There was a female hard pen calligrapher named Zhang Xiu. Her handwriting is really beautiful, but her personal style is strong, which is only suitable for appreciation, not for practicing copybooks!