I made something like that for my own blog. Wanted maps for my trips where I had recorded GPX files.
Used Mapbox as they allowed for easy tile customization. I wanted something that emphasized the path and terrain, but without labels and a lot of other details.
I think a key challenge for a FOSS solution is license to map tiles. Even OSM tiles have usage restrictions. It's fine if you only need something for yourself. But if you want to offer something to anyone...