Thanks for your comments. But no worries, I switched to Brave, which has qwant on their list, after realising that this request has been on for quite a while and Opera did nothing about it.
Use a descriptive and relevant title for new threads.
Be clear and concise when describing the problem. Be specific and remember to include important details, such as the exact error message or address of the site you're having trouble with.
Sorry for the past 1 year I have not fixed the Opera sync extension. Pity! I can't wait any longer! I finished the opera!
Passing on Chrome!
Bye, Opera! Closed topic!
If you come back on the future,
Use some online storage to back it up, then you will be able to use that Profile on any computer despite missing Extensions Sync.