Vivaldi does quite a bit of upstream development (for their team size), and it is as close to the original Opera as you're going to get. It is proprietary, thou

Vivaldi does quite a bit of upstream development (for their team size), and it is as close to the original Opera as you're going to get. It is proprietary, though (but their history w.r.t to treating their users right is better than everybody else, except maybe Apple).