If you look in the Bugs and technical issues in the sub forums to the right there is a pinned discussion about recovery options.

*Edit : Also you can disable cloud saves and you can set a Valheim shortcut to your desktop folder. You can also back-up world and character files.

Also I think the guy above is mistaken , look at the pinned topics here and in the bugs and technical issues folder. you likely have a save that was tagged "old".