Hey @zanzandora, good to see you again (just replied to your imagery tile crash in #46192 as well).
Two notes on the blockers:
ImageryProvider (just in case)
If you haven’t already, make sure you’re extending the ImageryProvider base class rather than using an object literal. As of Cesium 1.100+, POJOs will throw DeveloperError immediately. The key getters you need: tileWidth, tileHeight, maximumLevel, minimumLevel, tilingScheme, rectangle, errorEvent, hasAlphaChannel, plus a requestImage(x, y, level) method returning a canvas.
For mvt-basic-render’s style spec gaps (!in, nested booleans), that library only implements a subset of the Mapbox GL spec. You’d need to simplify filters or patch the renderer for those operators.
TMS ZIP for ion
The “not georeferenced” error is usually a missing or mismatched profile attribute in tilemapresource.xml. Make sure profile="global-geodetic" for EPSG:4326 or profile="global-mercator" for EPSG:3857, and that the BoundingBox matches the SRS. Ion is strict about that.
Recommendation
Given your constraints (visuals only, max performance, zero interaction), Plan B (server-side rasterization to TMS, then drape via ion) is the stronger path. Once the upload issue is resolved, you get clean terrain-draped imagery with no client-side vector processing. PR #13404 for native MVT is still in progress, so I wouldn’t wait on it.
Cheers!