Custom ringtones, alarms, notification sounds on Android 8.x+

Copy-paste your ogg/mp3/wav(?) file to:

• /sdcard/Notifications for notification sounds.
• /sdcard/Alarms for alarm sounds.
• /sdcard/Ringtones for ringtones.

If they then do not show up in your System > Sound > Notifications file picker, move those folders to /sdcard/DCIM/Media instead. So

• /sdcard/DCIM/Media/Notifications for notification sounds.
• /sdcard/DCIM/Media/Alarms for alarm sounds.
• /sdcard/DCIM/Media/Ringtones for ringtones.

If they still do not show up, reboot your phone.

I don’t really know why it did no longer work for me to put them in the sdcard rooted directories but I assume having installed Zedge before broke that. The default media files in Android 8.x+ images (at least for Pixel 3) are located in the product.img file.