Install APK from ADB and bypassing the prompt on Redmi
In addition to adb install, you can directly use package manager from adb shell to install apps. Place .apk files in /data/local/tmp and make sure files are readable, SELinux context must be u:object_r:shell_data_file:s0. Now:

~$ cd /data/local/tmp
~$ ls *.apk | xargs -I {} pm install '{}'


Another simple root solution is to use some file explorer e.g. MiXplorer to batch install apps. Select all .apk files and tap on Install from menu.