The trail Gränsleden/Rádjebalges connects Ritsem (Sweden) to Slahpa/Sørfjord in Tysfjord (Tysfjord kommune page about the trail). Unfortunately, there is no public transportation (and no road) from Sørfjord to the nearest road at Gåsluokta/Kjøpsvik, chartering a boat will cost thousands of Norwegian crowns, and the landscape does not permit hiking; indeed, usually people walk Gränsleden in large groups of at least 10–15 people (to share the costs for pre-booked boat transport). In Slahpa/Sørfjord are a wind power plant and two water power plants. Do people from Gåsluokta/Kjøpsvik work there on a daily basis, and is it feasible to hitch-hike over the fjord? Or is the power plant mostly unmanned? I'm quite sure they would take a lone hiker, but it only works if they are there in the first place.
Since there is a small village in Slahpa, I would assume that anybody who has to commute daily to the power plants at lake Bryn south-east from there would live in Slahpa since they cantake a road instead of commuting daily with a boat from Kjøpsvik, after which the person would still need a car to drive up to the plant.
Maybe there is a higher chance of a group hiring a boat that you can go along with than someone going there daily for work on his own boat.
There might be a chance however that there are daily boats with supplies going to Slahpa lodges and residents that you can tag along on.