@stateofreality
Have a look at this page. Before downgrade I did what they suggest on this page

https://forums.opera.com/topic/20590/how-do-i-reset-my-passphrase

@stateofreality

1. Download older version of Opera from their site
   https://get.opera.com/pub/opera/android/9100/Opera_91_6_4817_85486_Generic_Opera_arm8_LZMA.apk
2. You have to turn off settings in your phone, if they are activated. Settings/Security and privacy/advanced protection - turn off device and account protection, otherwise you won't be able to install it manualy. These settings are preventing installation of applications outside of google play store. Account protecton disabling can take up to 24 hours according to Google information. If you have not turned these features on, you can install that downloaded opera apk immediately.
3. Don't update until you know issue was fixed.
4. Sign into your account for syncing and enjoy.
5. Turn back on advanced protection settings if enabled before.

Hope this will help you. It worked for me.

@stateofreality downgrading to previous version did the trick. Sync working without issues. I won't update, till this be fixed.

Guys I have exactly same problem like you, except on Google Pixel 9 pro 512,same android build and opera version. Withou sync, working properly. After signing into sync, Opera immediately crashes.