Hello again Hello3,
Here's an update.
I downloaded and installed an app you suggested and it does eventually see the tablet. Is it right that it just looks like a window with a disconnect and connect button and the device name? it did have a music symbol and the bluetooth icon on it.
Samsung DEX is not working as it should be.
Managed to get it to send sound via that bluetooth app, or at least I thought but my laptop cannot hear it and there is nothing showing on the input devices.