My bookmarks are gone after the upgrade.
However, the bookmarks are not lost.
I found them on the computer under:
C:/Users/xxxx/AppData/Roaming/Opera%20Software/Opera%20Stable/Bookmarks

Further actions then:

• file opened with Opera gives a text file.
• Saved the file as a html file.
• Opera menu ►to full browser settings
• ►synchronization
• ►import bookmarks and settings
• ► favorites / bookmarks
• ► Bookmarks html file
• click on “import” gives
  

But there are still no bookmarks …
Wrong procedure or …?
Thanks in advance
GB48