Before the update it was possible to set up an FTP server with this: https://play.google.com/store/apps/details?id=com.oxsoft.ftpserver and copy files to the box internal storage on local network.
Sadly after the Oreo update the server allows you to connect, but the home directory content is empty and also you can't copy any files. I've checked permissions, reinstalled the app, but no changes.
So now after the update how can you copy files onto the box internal storage?
I am using mixplorer as ftp server Needs sideload
enable network adb debugging and adb push the files
Es explorer has one inbuilt. Just sideload the pro version as it's much easier to use with a remote becuase of dark theme.
Inbuilt ftp is the reason I'm still using ES
Also, you always have cloud options in most file explorers.
Xplore File manager is on the Play Store. Just upload you files to Google Drive, or Drop Box or any number of cloud storage services. If you don't know how to set up shared folders on your computer. Xplore will allow you to log in to either your local network or cloud servers. No FTP or other fancy funny named stuff necessary.
It's easier to go the other way around. Setup a FTP server on PC and use X-plore's FTP client function to connect to your PC and copy files between MiBox and PC. You can also use SMB share. This is more flexible for watching video. You can choose between downloading the entire video to MiBox or just streaming it (Kodi supports streaming video over FTP and SMB). Also downloading big files over FTP is usually faster than uploading them.
I am using IIS's FTP server on Windows 10 to share files with MiBox and a few other devices in my network. Filezilla Server should work as well. I also setup a Dropbox connection in X-plore as a backup way to share files with my phone or PC.