@MarkD73,

There are a few reasons that these devices may be appearing.

Normally, this behavior is the result of your mobile devices being connected to the network while the phone's 'Randomized MACs' or 'Private Addressing'. You will need to disable this option from your phone's and tablet's Wi-Fi settings.

You can always set an IP Reservation or MAC Binding to encourage or force your devices to connect to the network with a set IP address.

For your smart devices, the MAC address is normally listed somewhere on the device, otherwise most smart home manufacturers will provide a method to view the MAC address from within their smart home app.

You may also see devices listed as unknown if they are not properly reporting their name (common with cheaper smart devices); or can sometimes occur when traffic is passing to the network through a switch.