Here some recommendations for possible OPC UA Demo Clients:
Note: It is likely that you will need to enter contact details to download these files.
https://industrial.softing.com/products/opc-ua-and-opc-classic-sdks/opc-ua-demo-client.html
https://www.unified-automation.com/downloads/opc-ua-clients.html
https://integrationobjects.com/sioth-opc/sioth-opc-unified-architecture/opc-ua-client/