Would Scandinavia oppose a British Baltic entry?

Would a British move into the Baltic force the Scandinavian countries to enter the war against Britain?

No. After a decisive British naval victory, the Scandinavian neutrals would have little strategic reason to attack the Royal Navy and might instead seek advantage from Germany's weakness.

A Scandinavian declaration of war on Britain is highly unlikely. If the Royal Navy had just smashed the High Seas Fleet, Sweden, Denmark, and Norway would have little incentive to challenge the dominant maritime power directly. Their interests and grievances would differ, and Denmark might even see opportunity in Germany's defeat instead of a reason to rescue it. A British Baltic campaign depends on regional access, neutrality, and trade as much as on fleet combat. An anti-British coalition needs a persuasive strategic motive, which this scenario does not provide.