Hello Erin,
Great question! One of the more common use cases we tend to hear about is when there are operational LRS event layers that business stakeholders need to see as reference information in their Event Editor configuration but those users do not necessarily need to edit or are not allowed to edit those elements since they are maintained by other business units.
In this case, a viable approach to having LRS event information in the webmap is to publish those layers as map services without Linear Referencing capabilities enabled. In this scenario, since you are not leveraging the LRS server for the service you can impart whatever definition query on the layers you wish. Only the LRS enabled map image layers (map services) added to your web map in portal will respond to the temporal LRS capabilities. The reference layers you add into your webmap will show as a different layer grouping in the TOC and you'll still be able to leverage snapping to those layers for edits.
Hope that helps - If you have a more specific use case I'd very much like to hear about it. Thanks!
Amit @ Esri
