@ Enno -- My integrated GPU is Intel HD Graphics (ie. the 1st generation, older than your GPU), which doesn't work properly with the game. Luckily, I have a discrete AMD GPU that I could switch to in order for the game to render properly. But the GPU switching must be done before launching the game, because switching the GPU during gameplay has no effect.
That being said, like you, this game is the first & only one to date that my integrated Intel HD Graphics GPU (enabled by default) has problems with. Perhaps it's because unlike other Unity games that I'd played, the only 'Graphics Quality' options provided in the Unity settings panel upon first launch of this game are restricted to: Good, Beautiful, & Fantastic -- with no lower options such as: Fastest (which I prefer), Fast, & Simple.
Maybe the game developer @Fi Silva can consider making lower graphics quality options available, especially for players without a higher-end gaming GPU to switch to.