I have raised my morphs with a mixture of Springtails, fruit flies, frozen bloodworm and eathworm.
At the beginning, the morphs will stop eating for some time, even as long as 1 month. By those time, I would feed them springtails and fruit flies. Since these are smaller and moving, which might increase their appetite. Then later, I switched to feeding frozen bloodworm with tweenzer. In this case, it was very difficult, it took a long time every day to feed them. However, the result was great. Then I started feed diced earth worm pieces, this will be easier and healthier for the morphs, since these are nutritious and smell good.
Then, after 1/2 year on land, I started introducing the healthier and bigger morphs back to water. Which the feeding in water was much easier.
the good things about raising the morphs on land (sands and coconut fiber) was that I seldom need to clean up the tank.
Sometime the water in the water dish evapourated and drop back to the substrate. Which then, as the water accumulated, I useda syringe to remove the water from the substrate, which partially cleaned the tank. In the case of using soil, I think you will not be able to clean the tank like the above method.
I have also kept some amount of springtails in the tank, which helped the cleaning. I also had lot of plant in the tank.