1

leaving Germany's Lufthansa as the sole Western European-based carrier offering services to Tehran.

What about Alitalia?

2

They refer to the sole Western European airline
Other European airlines continuing to serve Tehran, including Aeroflot, Alitalia, Turkish Airlines, Pegasus, Atlas, Belavia, Correndon, and Ukraine international, are not considered WESTERN european airlines by the author of the article.

3

Other European airlines continuing to serve Tehran, including Aeroflot, Alitalia, Turkish Airlines, Pegasus, Atlas, Belavia, Correndon, and Ukraine international, are not considered WESTERN european airlines by the author of the article.

I don't know what said the article when the OP linked it (because I didn't read it then). However, I read the article today and, it doesn't say Lufthansa is the sole Western European-based carrier offering services to Tehran and I can't find any reference in the article talking about Western Europe Airlines. BTW, the article points out that Alitalia has flights to Tehran that was a point I was trying to point out with my post in #1.
IMO, to present (talk about) Lufthansa as the sole Western European-based carrier offering services to Tehran could be misleading as some people could overlook Alitalia and therefore my comment.
BTW, I think it's UM Airlines (not Ukraine Airways International) the Ukranian airline that flies from Kyev to Tehran at the moment.