What did I do last year, when I worked with recordings of classes through Whereby, I received the image of each classroom through the Input >> Browser and did the re-transmission to record in a restricted group on Facebook!
For each classroom I would open an instance of the OBS and re-broadcast it to a different Facebook group.
>> 4 classrooms >> 4 instances of OBS >> 4 restricted groups on Facebook where classes were recorded and thus are already published in a restricted way for students to watch later.
I use a 4.0Ghz i7, with 32Gb RAM, NVidia 1050 Ti, MB MSI Z97-G45 Gamming, Corsair SSD for the system and 2 more SATA Seagate 7,200 rpm hard drives.