@exussr said in Opera browser stopped saving cookies.:
But according to your link: URL opera://settings/content/siteData?
in fact, cookies were disabled.
But, I found this item in Settings, only through your link.
To get to it via settings, goto privacy and security, then 'site settings", then "additional content settings", then "On-device site data".
When you're on a site, you can click the badge at the left of the address field (usually the lock icon), click "cookies and site data", click "manage on-device site data" and then click "manage site data".
You can blame Chromium for these complicated changes.