Herewith latest DB Compatibility list :
*** EDIT ***
MongoDB is currently in BETA testing, so, will hopefully be included in the next NBU update.
As Marianne has stated, not supported as yet. However, as an interim measure you should be able to take a flat file dump of the Mongo DB and back that up as part of a normal filesystem backup.
I've currently got one MongoDB database which is running on Windows that I backup. This particular one is used for signage on Sony Bravia TV's. To back this up, we have a scheduled task that calls:
C:\Program Files\MongoDB\Server\3.2\bin\mongodump.exe with the following parameters --out C:\DB-Backups. This does a dump of the DB to C:\DB-Backups.
Not sure if your environment is Windows or Linux/Unix, but you could use mongodump as an interim method.
Hope this helps,