Hi Hugo,
The BeagleBone Black is the equivalent of a computer, running (usually) Linux.
Think of it like a PC. As a result, by default there is no MIB for it, but there is nothing to stop anyone from creating it, to run as a process.
It's a useful thing, I'm sure others would also have uses for some basics like temperature and CPU usage and other resource availability observable via SNMP.
There may be some free code out there to do it, otherwise it would have to be written by someone . Linux has SNMP libraries and a daemon.. so that would be worth investigating.
I have used Linux to retrieve SNMP counters but I've not done it the other way which is what you're asking for, so I cannot really help much further.