You should be able to rollback your phone to a previous release of OOS with them if for some reason you want to go back to an older firmware
Please note that on N10 crossflashing regional builds is no longer possible by EDL, flash is tied to device project ID. I therefore expect same to happen on N100. For reference EU devices project ID is 20883 while international devices project ID is 20881.
On the login prompt select "Other" in the dropdown menu and click on Next.
Wait a few seconds until main window shows up.
Press Start button so that it waits for your device to be connected
Power off your device
Maintain volume up and down buttons to get into Qualcomm EDL mode.
Plug your device to your computer.
Should you not manage to do that and have adb access, you can use adb reboot edl instead
Wait ~300 seconds.
Enjoy your brand new device.
Does this work on Mac or on Linux?
Unfortunately no, tool is Windows only. You should need at least Windows 7.
Why is my antivirus freaking out when unzipping the archive or running the tool?
In an effort to protect reverse engineering from being done (and by extension prevent conversion process like it was done on 6T and 7Pro), OnePlus now use VM Protect V3 in their MSM tools. As this tries to detect debug environment, this is seen as malicious behaviour by some antivirus.
How can I check my device project ID?
Use getprop ro.boot.project_name. This however involve having ADB access or access to OxygenOS to use Termux or whatever terminal emulator you prefer.
Ensure you're using the Qualcomm drivers linked above.
MSM tool is stuck on "Sahara communication failed"
Unplug your phone, get in fastboot mode, turn off phone, wait 15 secondes and get back in Qualcomm EDL mode. You can also try using a USB 2.0 port instead of a 3.0 one.
What is SMT Download mode?
Just don't try to unlock that mode, it will wipe your IMEI and your Widevine certificate if you use it.