(Hypothetical Concept) But is it possible to depend on a white dwarf as our power source? Provided we harness its 99% of energy? Can life be sustained?(If it is possible we can easily colonize an exoplanet which is located at a suitable distance from dwarf star)
The Dyson-sphere is gravitationally unstable. The planets have a circular orbit, but a the Dyson-sphere is a sphere. Where could it rotate? It doesn't matter, on the poles it would fall into the star.
The current technological reality is that the fusion energy, and then heating and lighting a planet with it, is not far from being possible. We could do in same decades, we would only need a peaceful, well-organized humanity for that :-)
But building a Dyson-sphere is far, far away. There is nothing from which it could be built.
However, a planet having life around a white dwarf is possible even without such things. The power what it gets from its Sun, increases quadratically with the recipe of the distance. I.e. if the planet is halfway to the star, it gets 4 times more power.
An imaginary solar system, whose star is a white dwarf with the power output of 1% of the Sun, may have habitable planets 15million km from it. (The Earth-Sun distance is 150million km.)