Here are the solutions. Click on Notation to see the moves, and Games for a list of the games.
Here are the solutions to all four problems, nicely explained by Volclus, in YouTube shorts:
In over 4 hours in front of the camera, Karsten Müller presents to you sensations from the world of endgames - partly reaching far beyond standard techniques and rules of thumb - and rounds off with some cases of with own examples.