the mapy.cz app already has all the Camino tracks (blue line) in its map, you don't need download anything.
Any mapping application that uses Open Street Map data has these tracks available to them as a layer that can be presented to a user. So not just mapy.cz, but OSMAnd+ and its iOS equivalents have these tracks. Some apps will allow them to be turned on an off. If all you want to do is follow them on the map while you are walking, you can do that.
If, however, you want to do any stage planning, they are not like a gpx track from the various sources, or a kml track from the
Centro de Descargas, the Spanish mapping agency. They cannot be edited to create a walking plan for a day which can then be used for measuring distances, voice guidance, off-route warnings, etc.
I know that an app like OSMAnd+ will allow you to create your own route, and so you can enable the walking tracks layer (which includes the Camino routes) and manually set up the waypoints along that route. That might sound cumbersome, but if you are familiar with how your mapping app works, it quickly becomes routine and is normally something that can be done in a few minutes.
If, like me, you use a GPS or GPS app for work or recreational reasons at home, you may already have the necessary skills, and will find this second nature. I worry more about those who are new to navigating off roads while walking. It is not that I don't think that they could acquire those skills, but it does need an investment of time to learn and practice them. When there are good, Camino specific, apps available these days, I do wonder whether it would be better to use one of them instead. Even if it means foregoing some of the features like off-route alarms or voice guidance available on a dedicated mapping app.
