Sorry, I have no such problem here, tested with
- this Fairphone 2 setup
- this USB OTG cable
- 2 USB sticks - 1x FAT32, 1x NTFS
- Edit: Logitech wireless mouse + keyboard combo
USB sticks get mounted and I can use the file browser on them.
NTFS is a positive surprise, back with Fairphone Open OS I used a Total Commander plugin by Paragon for this. Seems I no longer need that.
Edit: Mouse and keyboard work immediately after plugging their receiver into the USB OTG cable.