What is missing is either a DTH or a Edge driver that understands the manufacturer specifc clusters that the device is almost certainly using. Basically it speaks Zigbee as its network transport but beyond that its encapsulatibg all or parts of its communication in a proprietary format. Its not unique - lots of vendors do it when they feel they have extra functionality to convey not directly supported by the spec. Tuya does this with all of thier zigbee stuff and its why they need a custom DTHs on smartthings.
‘zigbee thermostat’ is a great little DTH if your manufacturer is not doing anything ‘unique’. But if that didn’t work you almost certainly need a custom one written to understand the device. As folks have already said at this point don’t bother trying to locate or write a new DTH that platform is on iys way out… Instead find out if anyone is interested in writing an edge driver for it.