I have a web map with a single layer added using the "Add layer from URL" method. The file is a CSV stored in Google Drive. I'm using this method because I want the layer to update once a week. The data change frequently.
In the web map settings, there is no option to configure the search settings. Does this mean it is not possible to set up search with a URL-based layer? If so, is there a workaround to allow searching of this type of layer?
If no search is possible, what is the best way to add a layer that I can keep updated regularly without too many extra steps?
Instead of adding from URL, try adding from file as described in this blog article:
https://www.esri.com/arcgis-blog/products/arcgis-online/mapping/use-google-drive-arcgis-online/
That covers both adding from Google Drive and updating.
The result is a feature layer like any other feature layer, so you can apply filters, etc. The layer can also be configured as the search source in ArcGIS Instant Apps.