How to correctly unmount a partition in Android 11

Hi all . Please tell me how to correctly unmount a partition? This is the team that used to work:

$ adb devices

$ adb shell

$ su

# phone:/# 

# cd /dev/block/platform/msm.sdcc.1/by-name/

# umount -l /dev/block/mmcblk0p25  ( userdata)

Regain your privacy! Adopt /e/OS the deGoogled mobile OS and online servicesphone

After I completely removed the system from the phone, I was able to unmount the partitions! I checked how it worked on the old version of /e/, everything worked correctly, perhaps this is a bug, I ask the developers to pay attention to this.