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This depends on server hardware configuration. Actually, a load tests should be performed to check how many subscribers or publishers can connect simultaneously with a proper video quality: What kind of server do you need to run a thousand WebRTC streams?
The server described in the article was tested to use 1000 subscribers simultaneously. More powerful server (96 cores for example) may pass the test for 2000 subscribes, but it should be tested.
If you need more subscribers, you should deploy a CDN. For 10000 subscribers, you need at lease 5 edge servers (2000 subscribers per each). Please read this article about a basic CDN configuration.