WazzapMigrator is compatible with OnePlus 6 before its launch :D ref. https://www.wazzapmigrator.com/changelog/2017-08-18-000000/android-o-compatibility 
If you can't find the Media folder when using iBackup Viewer please check in here too AppDomainGroup-group.net.whatsapp.WhatsApp.shared > Message > Media Please note: there are 2 Media folder, you need the one inside Message folder
WazzapMigrator is compatible with Samsung S9 before its launch :D ref. https://www.wazzapmigrator.com/changelog/2017-08-18-000000/android-o-compatibility  
Unfortunately WhatsApp just released a new bugged version (2.18.9) that doesn't restore from local backups, like the ones created by WazzapMigrator and WhatsApp itself. In order to fix this: just install WhatsApp 2.17 as explained in here.
New WazzapMigrator 3.2.6 gives you the ability to hide or show WhatsApp images from the Android gallery! Just remember to restart your phone after.