How to provision a Mitel 480G/485G with Shoretel firmware (v802/803) to ringcentral

These phones are now supported on RC with autoprovision phone per (https://support.ringcentral.com/article/certified-supported-deskphones-ringcentral.html#mitel). However, the instructions given by the RC admin portal wizard and also on https://support.ringcentral.com/article/assisted-provisioning-mitel-deskphones.html will not work if your phones are on older shoretel firmware. I spoke with Mitel SIP phone support and here are the steps that worked. Sharing for anyone who is trying to convert these phones to RC.

1. Make sure the phone is added as a device in the RC admin portal using the mac address and selecting the correct model - see steps 1-7 only on https://support.ringcentral.com/article/assisted-provisioning-mitel-deskphones.html if you aren't familiar with adding devices to RC admin.
   
   
2. Factory reset your 480G/485G by pressing Mute then 25327# while on the idle screen. It will pop up asking if you're sure you want to clear the configuration. Press Clear softkey.
3. The phone will reboot.
4. When back to the idle screen, press Mute then 73887# to access settings
5. Navigate to Services > Config server
6. Clear any existing provisioning/config servers and put in this IP address: 34.110.141.137 This is a conversion server that Mitel SIP phone support team gave me which hosts the ringcentral firmware for these phones.
7. Press save and back out of settings until you see an Apply softkey on the bottom of the display at the main settings menu. Press Apply.
8. The hone will reboot. Allow it to reboot fully, it may do so a few times.
9. Eventually you will see a message in the top left of the phone that says "Dial 400 to switch to RC", and extension number 1000 in the top right.
10. Lift handset or use speakerphone to dial 400 and press DIAL/CALL.
11. The phone will say call failed and give a busy signal, but it will also say "Upgrading" in top left corner. Do not press anything or power down while it downloads the firmware. This will take several minutes (~10+ min) and reboot numerous times.
12. After the 1st or 2nd reboot, you'll notice your phones switch from showing the Shoretel logo during boot to the Mitel logo on a dark blue background. This is how you know you're on track.
13. Once it's done with the 3rd or 4th reboot, the phone will come up provisioned!