Livestream with BM Atem Television Studio

Our high school would like to livestream graduation this year. Last year our principal purchased BM ATEM Television Studio, 2 cameras, SDI cables, monitors, and our AV Production class, has used it for recording events, etc. They are just starting to try livestreaming. They have tried to livestream to YouTube, but cannot get it to work. After reading and watching videos, it looks as if we cannot livestream with the switcher without another piece of hardware like the Web Presenter.
I was told we can use "Livestream.com"software with the switcher, but we did not want to pay for it for this one event. Is OBS similar, and can you livestream using it without Web Presenter?
I honestly do not know enough about this equipment to know if I'm asking the right questions.
Thank you for any help!

You can use the web presenter with OBS... But...
There are known issues as the WP compresses the video ( and it scales it down to a 720 signal to deliver it over usb2)
Which OBS did have an issue ( but an update might have fixed it)

If you want to stay with BMD it's the webpresenter.

Otherwise you have usb3 devices like..
AJA U-tap SDI
Magewell 32070 SDI
Yuan PD570 SDI
Which all function the same as the WP.

Or you can install a hdmi /SDI capture card inside a pc and use it with OBS.
BMD's decklink mini recorder card will give you a single input which you can
use with the pc to stream from ur switcher.

.all the above can be seen by OBS, and other suchlike s/ware

Or you could choose a hardware encoder and streamer, like a vidu pro. Livestream pro, teradek bolt.
Or devices like ephian web caster X2, startech usb2usbcaps
which will all stream to the various platforms you mention.

Which version of Livestream TV Studio are you using? If it´s the old non-HD-version you can plug it to your computer with USB. For the newer one you can also buy a BM Ultrastudio Mini Recorder if you have a computer with Thunderbolt or a BM Decklink Mini Recorder if you use a computer with PCIe (Desktop), both for about 140 EUR/dollars. You connect SDI out of the TVStudio to SDI in of the Mini Recorder and you get the signal to the livestreaming software.
There is even a USB 3 version called intensity shuttle but it doesn´t work at every computer.
With mini recorder you get a better quality than with webpresenter which converts every signal to 1280x720.