I have been using A* for a Pure ECS game.
This is an authoring component I made and have been using for awhile: Current state and plans for ECS integration? - #41 by Curtis
The only caveat I have run into is when you want to use features that do stuff to the graph, like Navmesh Cut, you have to do a bit of custom work to bridge the Entities and GameObjects. For example, if you place an Entity building but need it to cut the graph, you have to create a system that will create a GameObject Navmesh Cut at the building location. I think it would be a similar situation for the Grid Graph equivalents.