The PC using OBS is under the firewall.
If there is an IP or domain list that needs to be allowed for OBS streaming, the firewall wants to allow it.
Do you have any related information? If so, where can I find it?
OBS is running locally. a typical firewall blocks a variety of inbound network traffic, but often allows unrestricted outbound traffic to the internet
OBS Studio allows you to configure where you send streaming traffic. and each stream destination has its own unique ingest IPs/FQDNs as koala mentioned.
So you need to clarify what you mean by "The PC using OBS is under the firewall."
-are you taking about a local operating system firewall?
or
- do you mean a corporate style business class network and firewall, that is restricting outbound streaming traffic?
if the latter, what you need to do is go to the streaming platform you intend to use (YouTube, Twitch, Facebook, etc) and get their latest documentation on stream ingest servers (ports, protocols, IP/FQDNs, etc). And realize that the list of ingest servers will change over time, and will vary by geographic region