Geomagnetic power generation has indeed been tried. Once, a country launched a small satellite. There is a metal wire several thousand meters long hanging under the small satellite, which is orbiting the earth at a very high speed (about 10 km per second). As a result, it seems that a very large amount of electricity is generated (it is no problem to electrocute a person). However, because cutting off the magnetic induction line prevented the satellite from moving at a uniform speed, the satellite soon crashed.
However, I personally have an idea to tie wires around the moon with nanowires. Because the moon itself is very massive, and it is moving away from the earth at a speed of several meters per year, there is no need to worry about being dragged down by the magnetic field, and such a long distance can also generate terrible current ~ of course, the technical conditions are limited. Now the longest nanowire may not exceed 1 m, but the distance from the earth to the moon is nearly 400,000 kilometers.