Demo page only works partially, many maps don't show

Problem/Motivation

Only some maps load on the Leaflet Demo page at /admin/config/system/leaflet-more-maps/demo.

Steps to reproduce

Visit the Demo page and see that some maps don't load. Many maps require an API key to work, so that they don't load makes sense. But also some free maps don't load.

On the Demo page, only these load, after patching Stamen maps (see 📌 Stamen map tiles moving to Stadia hosting and will no longer be available at old URL Needs review ):

• Stamen Toner-Hybrid
• Stamen Toner-Labels
• Stamen Toner-Lines
• Stamen Toner-Lite
• Stamen Watercolor

Proposed resolution

Figure out why some free maps don't load, and make them work again.

Remaining tasks

User interface changes

API changes

Data model changes