In the article:
"Now, in addition to some carriers in Europe, it appears that T-Mobile/Sprint in the United States is also blocking iCloud Private Relay access when connected to cellular data."
Though as far as I understood the European carriers voiced complains but did not act, thought UK carriers did (which isn't EU anymore).
Tbh. the article is just not very well written, I also first thought the article implied that T-Mobile US is an EU carrier operating in the US (it isn't, it's an US carrier owned to around 43% by an EU carrier, with which it shares a bunch of thinks, like trademarks).