You won't be able to until Cisco updates LMS to add the 5585X. LMS bases a device's manageability primarily on the device's SNMP OID. If the OID doesn't match the list it checks, it won't manage the device.
There's no public announcement of future support but this particular device has been inquired about before and is overdue for support by LMS, for what it's worth.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...