Drop Leaflet, move everything to Mapbox GL
This is nothing against Leaflet, which remains as awesome as ever.
However, for easier maintenance and enhancements, it would be best to limit our map preview technology to a single type.
Upgrade of Mapbox GL beyond 0.33.x will require using a different JSON fetch handler; the one we are using here has been removed.
When we do this, we likely need to bring in babel and support at least some polyfills.
However, instead of other bundlers, we might be able to leverage (esbuild)[https://github.com/evanw/esbuild].
maybe https://github.com/maplibre/maplibre-gl-js ?
maplibre-gl-js is certainly an option and avoids some of the issues around Mapbox tokens once mapbox-gl-js 1.13 is no longer being maintained and only upgrade path there is 2+.
Another alternative would be OpenLayers like mbtileserver-rs