Tried to followed this procedure: Fairphone Open 17.06.4 (Android 6.0) release
One of the workarounds but I stuck ad the adb sideload step. 
adb sideload fp2-sibon-17.09.3-ota-userdebug.zip
opening 'fp2-sibon-17.09.3-ota-userdebug.zip'...
connecting...
falling back to older sideload method...
error: closed