Workspaces don't help much. It doesn't explain what it is. Neither it is like a tab container like firefox where each session is different and isn't in relation to any other nor it is a session manager as it overlaps and mixes everything. I tried it many times but avoided it ever since.
And for "And Chromium discards tabs that are kept in the background for some time." I don't understand why you are focused on Chromium when I am using opera which has its own mechanism and structure different from chrome, or brave, or even Vivaldi. I requested something you didn't understand maybe you arent using opera as much as I am across on any platform for work. I have to take the help of firefox which does provide some sense of support to power users and even google understood it through chrome tab grouping. Opera team doesn't understand it, old users.
The saddest part is that there is no such addon in opera store that does give control to users about tab suspension or hibernation without closing them and letting them keep it the way they were before the closing of the browser. And those that exist are outdated, not updated, or lose all the tabs. Firefox has created many extensions to support users by themselves. Opera should also have done it apart from the default adblocker and VPN both of which doesn't do the job as promoted.