The built-in terrain generator in Mountaneous/VeryRough setting comes close, but is not coded to have fjord-like structures. So here is a West Norway heightmap
(2048×2048) made from Public Domain USGS data, and placed into the BaNaNaS system.
The heightmap encompasses the niveaus 0-1500m, linearly distributed onto the 15 height levels of OpenTTD. So, the height will be clipped in the east, giving the player a bit of flat space to toy with as well. Note that the value of industry_platform
tunable (“Flat area around industries”) should be low: It seems the industry generator will not touch the heightmap to achieve the desired flat area, but rather relocate an industry until it fits, leading to an absurd placement of all industries on the right half of the map with industry_platform=4.