As there are so many posts about this topic and it's getting a bit out of hand, I'll create one central place where we can talk about this stuff and share updates.
If there are very big updates, I might create a new post as the new megathread but for now, please don't create new posts for updates but post them here as comments.
Latest news: AVROTROS (the Dutch broadcaster) released a statement. The full statement is in the comments but roughly, they state that against made agreements, Joost Klein was filmed directly after getting off the stage and getting to the greenroom. He indicated he didn't want to be filmed, but this was not respected, leading to a threatening movement from Joost towards the camera, but he did not touch the camera women. This was the whole incident leading to the investigation by EBU and police, according to them.
Previous rumors also stated it was an israeli journalist harassing him.
There is a video of the Israeli song-writer doing exactly this. There was a couple filming and joost walked behind them and you can see the song-writer harassing joost.
Those were rumours and all parties have said that no Journalists or other delegations were involved. It was a member of the official Eurovision producing crew.