I tried to get multi-user support for my Android 7.1.1 AOSP emulator based on Ubuntu 16.04 64bit. Build starts with lunch aosp_x86-engand after the emulator with emulator64-x86.
I tried this solution, but without success:
adb shell
su
setprop fw.max_users 5
The icon is displayed for the first time when I erase the status bar, but disappears when it is released:

Same as here :
adb shell setprop fw.show_multiuserui 1
adb shell setprop fw.max_users 4
I also tried adding an adb user , but without success. After executing the commands, I test it using:
su
pm get-max-users
result:
Maximum supported users: 4
- ? ? , 4 ? , ?
!