Who succeeded Qianlong as the Jiaqing emperor?

The Qianlong emperor was succeeded by his 15th son, Yongyan, who took the reign title Jiaqing.12

Qianlong announced his decision to designate Yongyan as his successor on October 15, 1795, out of respect for his grandfather, the Kangxi emperor, whose reign had lasted 61 years. Although Jiaqing officially assumed the title in 1796 following his father's abdication, Qianlong retained real power until his death in 1799. During this transition, the Jiaqing emperor was largely confined to ceremonial duties while the corrupt official Heshen maintained significant influence. It was only after his father's death that Jiaqing was able to arrest Heshen and begin exercising his own authority.132