Have heard some good things about Streamyard. I know of a few groups that like to use OBS or vMix and feed into Restream (https://restream.io) to reach multiple platforms simultaneously (while maintaining a high-level of broadcast production). Alternatively, I'm also aware of Castr (https://castr.io) but don't have any experience with it. Oh and there's also Aircast (https://airca.st) which will also essentially clone your stream from one initial platform to many others.

I've gone the simple route in the past: Live stream on one platform, then publish the finished video everywhere.

OBS is the free tool I see mentioned for live streaming most often; it got recommended Capiche's discussion about the best tools to edit videos, though it takes some workarounds or hacks to stream to multiple sites at once (StackExchange recommends either running two instances of OBS at once, or to run nginx locally and use the server to duplicate your stream.

Otherwise, another service that the Wistia blog recommended is Crowdcast, which they paired with OBS to build the streamed video content, and then used Crowdcast to both live-stream the primary video and replicate it on other platforms.

Hi, at the university where I work we use Microsoft teams, also for webcasts, but there is still some issues with the combination of people speaking in the microphone and a video with sound from a computer. So for the better experience we just use Wirecast and we stream to Youtube where visitors can also ask questions through the chat.