Download MIUI V11.0.11.0 China Stable Fastboot ROM for Redmi 8 from here.
File name: olive_images_V11.0.11.0.PCNCNXM_20200516.0000.00_9.0_cn_3372a46fcc.tgz
Device: Redmi 8
Codename: #olive
Region: China
Version: V11.0.11.0.PCNCNXM
Android: 9.0
Size: 2.7 GB