I have another geopackage that is from a high resolution tif tiled at zoom level 21. Adding overviews to it with gdaladdo enabled it to render at lower zoom levels, but it still needs to be zoomed in on unlike the geopackage included with the sample. Additionally, once you zoom in far enough to start seeing individual tiles load, the load times for each tile are very long. The source tif loads much faster.
Having underscores in the raster table name made the layer not load
I have an example project I can send, but it is too large to attach here. Is there another way I can send that?