As you have already mentioned, the specific devices are not supported. That said, you might want to consider taking a look at our list of 3CX Supported devices here: https://www.3cx.com/sip-phones/
If the devices you posses cannot be used and acquiring a new set of devices isn't an option, maybe exploring the possibility of switching over to softphones is worth looking into. 3CX provides a Windows App, a Webclient (in web browser) and also an Android and iOS App.