I doubt if that train is still running that far. Seat61 doesn't mention it in any case but that may also be because there's no onward train connection. Did you ask Serbian railways?

No. Do you have an Email?

https://www.srbvoz.rs/en/

I found it! Thanks. I’ll write them an Email, thank you!

Highly, highly unlikely that any train will run over the Serb-KOS border. And as this is the IR-forum: IR is not accepted in KOS! But local fares are very cheap. They use EUR for cash payments

Interrail it is not accepted in Kosovo? I didn’t know that, thanks. But I would not say that there is no train from Serbia to Kosovo. If Serbian Railways offers one train from Pristina to Skopje, why they don’t offer trains from Serbia to Kosovo?

They don't. That is (or was?) a co-operation between Kosovo and North-Macedonian Railways.

The serbian Railways write in their international Timetable that this train is still existing.
https://www.srbvoz.rs/en/timetable-kurir/

The serbian Railways write in their international Timetable that this train is still existing.
https://www.srbvoz.rs/en/timetable-kurir/

I don’t know if the train is running at the moment. But just because a train is shown on the website srbvoz, it doesn’t mean that it is operated by Serbian Railways…
And this train is/was definitely not operated by Serbian Railways as a previous poster already said. Would make no sense at all (neither political nor economical...).

Kosovo railways agree:

http://www.trainkos.com/sherbimet/transporti-i-udhetareve/orari-i-trenave/

The problem then is how to get to Skopje.

There should be a bus from Beograd. Otherwise there are several departures per day from Sofia to Skopje (bus).

my plan is to go from Beograd to Kosovska Mitrovica Sever, and from there to take a bus to pristina. From there I want to take this train to skopje

If you arrive in Beograd, check if the train is running. If not there should be several buses per day going to Kosovska Mitrovica…

The train didn’t run when I was there in Sebtember. Don’t expect an answer from Kosovo Railways. But Macedonian usually respond within a few days.

The reason why Serbia railways listes the connection in their international timetable, is because Serbia still thinks they own the Kosovo, and the state railways participates that propaganda.

What train didn't run? The train Kraljevo - Kosovo or the train pristina - skopje?