You can sign the petition if you are a Danish citizen with your MitID.

I was surprised when I couldn’t sign the petition because although I’ve been a resident for a decade, I don’t have the right to vote in the general election.

One of the more baffling systems in the EU. I’m still expected to vote in Belgium, a country I left 25 years ago, and only allowed to vote in local and European elections, not national ones, in Denmark.