Just out of curiosity, can you tell you can't generate or check by yourself the matter of the availability of video content without using a proxy, maybe by engaging multiple non-network heavy parallel requests on the side of your server? I think I will check the issue and the available Twitch available API endpoints in more detail later.

Twitch names their server clusters with IATA, yes.
Twitch has many ingest servers where you send your stream and they all forward it to the main one which is in San Francisco, CA. So no matter where you stream from, it always goes to San Francisco.
Now, when a broadcaster starts his stream, he gets assigned a set of server clusters (for example: san francisco, frankfurt, prague, miami) and a set of server nodes (video12-video20, video36-video50, on each of those servers). When users connect to those servers, those servers pull the data from San Francisco and serve it. It always originates at San Francisco. It's their mother base.
But even if Amsterdam and London, or video2 and video71 aren't assigned to broadcaster, it doesn't mean users can't connect to them.
You can. Using my extension. If user connects to a server/node which is not assigned to the broadcaster, it still works like it is. The server pulls data from San Francisco and serves it to users on this node.
That's why it's potentially disruptive. When that happens, users are using server resources which are not assigned for this task, and may cause the "legitimate" users experience issues.

There is no way of knowing what servers and nodes are available to a broadcaster, unless you connect to Twitch API (Usher) from each location where Twitch has their servers:
Level3, edgecast, san francisco, seattle, san sose, chicago, washington, new york, los angeles, miami, stockholm, london, amsterdam, paris, frankfurt, warsaw, prague, sydney, hong kong, seoul, tokyoTwitch automatically assigns you to the closest available node based on your IP geolocation, so unless you have TOR/Proxy/VPN, there's little you can do.

The way I described (with proxies around the world) is safe for Twitch because it uses their own network balancer.
If a broadcaster has only London and Amsterdam and you query the API from Korea and Washington, you will still get assigned to London and Amsterdam.

I like Chatty and Livestreamer

any chance you could look at a livestreamer plugin that would allow to choose twitch cluster so I don't have to?

Why did you subscribe to orange.pl? Afaik there is no area in Poland where orange.pl is the only available ISP. Poland has far more small regional/metropolitan ISPs than France.

Orange (Neostrada) is the only available ISP in countless amount of places in Poland. I live in a big city and the only ISP I can have in this HOUSE (there are like 4 other for flats in my area) is Orange.

any chance you could look at a livestreamer plugin that would allow to choose twitch cluster so I don't have to?

I don't think that's possible without modifying livestreamer source (which I believe is in Python?) and it would take me a lot of time.

You should just ask them to connect you, they may ask you to pay for the connection but that will work. I've done that dozens of time from flats where orange.pl was supposedly the only crap available.

Why people in France, on this forum have a problem with Orange and Twitch?
Twitch just recently opened a new server in Warsaw (waw01) and I have 330 ms ping to it, with download speed 50kb/s. This ISP doesn't make any sense.

Hi

Thank you a lot for your extension.

We have Orange ISP too in France...
Orange.fr and Orange.pl have both problems with Twitch : https://lafibre.info/peering/perring-orangetwitch/

I'm using Free.fr ISP and Free has the same problems...

I am on Free.fr too. I tested all the available servers, and Amsterdam, Level3 CDN and Chicago seem to be the only ones that work properly.

On the other servers, at best it buffers every 3-10 seconds, at worst the video does not even display (it buffers indefinitely).

For me it's Stockholm