For 500+ attendees, I don’t know any conferencing software. For me, this is more a streaming scenario.
Owncast for example had no issues with 200+ users, I am not sure about 500+: https://owncast.online/
Owncast supports handing off your video to any S3 compatible storage provider as well, so you don't have to worry about your local bandwidth. And depending what provider you go with, you can do this pretty cheaply. It scales nicely. https://owncast.online/docs/s3/
Not only is the Raspberry Pi supported, you can use its dedicated hardware for accelerated encoding! You might just get better video performance out of a Raspberry Pi than you would other machines you have around. https://owncast.online/docs/codecs/#raspberry-pi
Very nice, plenty of contributors, OpenCollective support, a live demo server but even https://owncast.online/donated/ that's impressive.
I guess to compare back with PeerTube there is no federation nor video replay with transcoding features for now.
There are other options. A lot of people who host Owncast instances do it on DigitalOcean, Linode, Hetzner, or even from their own homes.
As for bandwidth, most people who use a $5/mo Linode or DigitalOcean machine are given enough bandwidth where they're fine with the audience they have. However, if you plan on growing your audience to something really large, or running your server from home where you are limited with bandwidth, you can use external storage providers (B2, DO, Linode, Wasabi, etc etc) to distribute the video instead. But very few people need to use this feature. But if you did, it would only be ~$5/mo most places.
okay I actually got it to work the only issue I am having now is putting it on my dockers. I can go into the terminal & run it but I don't want to always go into the terminal to run it. I am very new to linux anything TBH. I want to add it to my dockers so I have quick access to it & the directions on the website are kind of confusing. I am following the quick guide in the dockers area & I am not really sure on how to save the blueprints doc to config.yaml though.
Owncast is looking promising. Open source self-hosted alternative to Twitch. So as a streamer you get your own domain and VPS for $5 or more depending on your needs, point your OBS to it and off you go. And you can get listed on the Owncast directory or stream unlisted. At any rate, there's no shitty Amazon or Google overlord forcing ads on your viewers or telling you what you can and cannot do.
It's very new though and early in development, so not quite ready to replace Twitch imho. But it's quite exciting and I'm curious where this or similar projects are gonna go to take back control.