In case it helps anyone, I have a fork of mapbox-gl-js where I've ported Leaflet's support for AGOL tiled services GitHub - maphubs/mapbox-gl-js: Fork of Mapbox GL with support for ArcGIS Online raster tile sources For now, it only works with ArcGIS Online services with cached tiles. You can see an example of it in-action here: https://mapforenvironment.org/layer/info/148/Amazon-Human-Footprint#3.37/-3.39/-63.51 I've also used Esri's open-source Terraformer project to convert MapServer or FeatureService queries to geoJSON for display on Mapbox GL, all in the browser. However, my current implementation is limited by the maxFeatures limit of the rest API query, and can be a bit slow for larger datasets. Also newer FeatureService query endpoints can generate GeoJSON directly.
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