Among contemporary calligraphers, what are the most suitable for beginners to learn brush calligraphy?

Beginners should practice the Jiucheng Palace in Ou Yangxun or the Diligence Monument in Yan Zhenqing. Because you want to lay a foundation, you must practice regular script well. China has a long history of calligraphy, and contemporary calligraphers also learn from ancient calligraphers to improve themselves. I study China language and literature. Our calligraphy class is a specialized course. I like calligraphy myself. I have been practicing Ou Yangxun's Ninety percent Palace. I suggest you choose Ou Yangxun or Yan Zhenqing to practice regular script according to your preference. I hope my answer is helpful to you!