Mounting a ext4 formatted sdcard on Android Marshmallow
UPDATE an better solution https://android.stackexchange.com/a/204616/119381

First steps:

I could mount and use my pen usb with ext4 after install [1] but still bery tricky (need root) I need first do 

   adb shell
   su -
   mount -t ext4 /dev/block/sda1 /mnt/sdcard/usbStorage/sda1/


and after umount and mount sda1 with stickmount.
For some reason stickmount (when works alone) says that device is mount but it is not , I need mount it as root ... , after I mount it , stickmount do the rest of the work ... 

[1]
https://play.google.com/store/apps/details?id=eu.chainfire.stickmount&amp;hl=en

Update 2017-12-26:
After read: 
https://android.stackexchange.com/a/131839/119381

https://source.android.com/devices/storage/config.html
and 
https://stackoverflow.com/a/28018008/778517

I did is and works on kodi and other apps , 

adb root
adb connect 192.168.1.160
adb shell mount -o rw,remount /;

adb shell


(edit) /fstab.hardware and change vfat to ext4

vi fstab.rk30board 
/devices/30040000.otg*     auto ext4 defaults      voldmanaged=usb:auto

mkdir /data/media/0/usb1
mount -t ext4 /dev/block/sda1 /data/media/0/usb1/
mount -t ext4 /dev/block/sda1 /storage/emulated/0/usb1/


I also used [root] adb wireless from google play https://play.google.com/store/apps/details?id=com.dshylai.adbwifiwidget&amp;hl=en but now I see that I have more options 

More info:
https://forums.lenovo.com/t5/Moto-X-Play/Android-ext4-support/td-p/3262765