Oreo final just dropped. If you can't wait for the update to arrive (or you are stuck with some old Nougat firmware) in your country you can flash it manually. Doing that leaves Knox intact
1. Check your current firmware, you need to have OXM under your "Service Provider SW Version" and firmware build AQL5. If you have all of that you can skip to point 4.

2. If you don't have OXM Multi CSC you need to switch to it. It requires you to wipe your phone entirely, you can also lose some carrier specific features. You need SmartSwitch installed to get the needed drivers, SamFirm: https://forum.xda-developers.com/attachment.php?attachmentid=4243214&d=1502879950 and Odin: https://forum.xda-developers.com/attachment.php?attachmentid=4168915&d=1496396854

- Download firmware file with SamFirm (put SM-G950F in Model field, PHN in Region field - it will download the needed firmware version), check the "Auto" checkbox and then click on "Check Update".

- Select "Check CRC32" and "Decrypt Automatically", click on "Download", wait for it to finish

- extract the ZIP to the folder when you extracted Odin (I recommend using the shortest path without spaces or some special characters), copy the file which name begins with CSC to the desktop, open it with 7-zip or whatever else you use for archives and extract file with .pit extension, put this file to folder with Odin.

- Open Odin, reboot your phone to Download mode (Vol- + Bixby + Power), accept the warning and connect the phone to PC, Odin should detect it.

- Assign firmware files to their designated slots - AP* to AP, BL* to BL, CP* to CP, CSC* to CSC, you don't do anything with Home_CSC file yet.

- Switch to Pit tab, accept the warning and then select the .pit file you extracted, switch to Options tab and make sure only these checkboxes are checked - "Auto Reboot", "Re-Partition" and "F. Reset Time"

- Make sure you have your files backed up and click Start

- Wait until Odin finishes it's work (it will show green banner with Pass and reboot the phone)

- Phone will start and then reboot to select correct CSC based on your SIM card. After it's done setup the phone and proceed to next points.

3. If you have OXM CSC but no AQL5 firmware do everything as said above, BUT

- Instead of CSC* file, assign Home_CSC* file to CSC slot

- skip the whole .pit part (don't extract the file, don't select it in Odin) - Make sure "Re-Partition" is not checked

- Click Start and wait for the process to finish, in the end phone will start normally, data will be intact

4. If you have above sorted out, it's time for the Main Attraction.

- Download AQL5 to CRAP update.zip: https://androidfilehost.com/?fid=673956719939818342

- Put in on your SD card (it's needed here) - Reboot the phone to recovery mode - switch the phone off, press Vol+ + Bixby + Power, release power when you see the splash screen but keep holding the rest. Blue screen will appear, when you see an Android on it's side and a warning sign hold Vol- button for a few seconds, you will see recovery screen with a few options.

- Using volume buttons select "Apply update from SD Card" and press Power to select option

- Select update.zip you placed on the card and press Power

- Wait until the phone completes the update. It will reboot automatically.

** Alternatively, if you don't have a free SD card you can use ADB sideload.

- Get Android platform tools: https://developer.android.com/studio/releases/platform-tools.html and Google USB driver: https://developer.android.com/studio/run/win-usb.html

- Copy update.zip to the folder where you extracted platform tools (again, shortest path possible recommended)

- Reboot phone to recovery as described above, select the option "Apply update from ADB", connect the phone to PC, open command prompt that has the directory with the update.zip and adb selected

- run "adb devices" command (without quotes) and check that the phone shows up there

- run "adb sideload update.zip" command. Update will be uploaded to the phone and applied

- Wait until the phone completes the update. It will reboot automatically.

Congratulations, you have the Oreo firmware without waiting for it. https://i.imgur.com/gHboqEY.jpg