I think I got excited too early. I too am having issues eventually with this factory reset procedure, and eventually end back up at the certificate error.
1. I power on grill, and open Menu -> Settings -> About Grill. Shows v2.0.0, config ver: 06.008.
2. I hold Ignite button until Traeger logo appears.
3. After screen shows it's powered up, I power off. Wait 5-10 second, and power back on. (I've tried the following steps with display both on and off)
4. Open Menu -> Settings -> About, and grill shows version 01.01.06, config ver: 06.008.
5. I open WiFi settings to make sure it's running on it's own AP, and no network to forget.
6. After uninstalling phone app (Android 10), I reinstall, sign in, and start WiFire setup again.
7. Phone connects to grill, and sends my WiFi info.
8. Grill connects to my WiFi and maintains connection.
9. My phone reconnects to my WiFi network.
10. I'm presented with the "Nickname your grill" input.
11. I enter a grill name (I've been trying different names, just in case), and the app immediately goes back to main screen.