I believe that Microsoft uses Akamai to distribute their various patches. They have servers all over the world for software delivery. This includes software updates.
Navifirm+ author says it will be updated in 2nd Quarter 2016 to use the new servers.
Mr Crab seems to be able to find anything, if you know the model and product code. Nokia Firmware MrCrab.Net Never click a 'download now' link, they are ads.
Links to firmware are generated and are temporary. They sure like to make things difficult.