Preface - I have not done much in Librenms with Mibs and yaml’s, https://community.librenms.org/t/emerson-liebert-vertiv-pdu-not-showing-power-graphs-for-individual-ports-2/ is about it and that was fairly simple due to a preexisting yaml file i could extend.
On the other hand I do understand why not all of the thousands of vendors and tens of thousands devices ware already included in LibreNMS - because its just a ton of work and there are not enough people doing work and just too many things in queue already…
A mib can contain hundreds of Object IDs that might or might not change based on hardware or software releases or license features. If you don’t have hardware to test its quite difficult to develop a yaml file (which maps oids to predefined interfaces) which will work with a single device let alone a group of devices.
Now I think the starting point is the documentation (Intro - LibreNMS Docs) which is unfortunately not labeled very clear - basically what is meant by new OS here is any new device (type).
What you basically have to do is to look at your device, check what information you want to see, check which OID provides this information and add that in the appropriate yaml file section.
O/c there is a bit more to it, but thats the basic steps.
I would recommend to look at the other discovery yaml files to find example how it is done, ideally for a similar device type or if you cant find/have any then for another piece of hardware that you have…
Hope that helps,
cheers
p.s. If you have no idea of snmp/mibs and regular expressions then you might have a hard time … that excerpt is actually fairly simple (to read, not necessarily to create), it reads a string with a regular expression into the SysDesc field of the OS part, then reads an OID into features (called by name instead of number representation), same for the hardware details…