Learn German: Die Journalistin informiert mich, warum der Bericht nicht aktuell ist. - The female journalist informs me why the report is not up-to-date.

Because warum starts an indirect question. Indirect questions act as subordinate clauses, and in German, subordinate clauses always kick the conjugated verb (here, ist) to the very end of the clause.

Is the question word warum acting like a conjunction here?

Exactly! If this were a regular direct question, you would ask Warum ist der Bericht nicht aktuell? with the verb right after the question word. But when you attach it to another sentence to make an indirect question, warum acts as a linking word (a subordinating conjunction) and pushes the verb to the end.

Wait, doesn't aktuell mean "actual" or "actually"?

No, aktuell is a classic false friend! It looks like the English word "actual", but it means "current" or "up-to-date". If you want to say "actually" in German, you would use words like eigentlich or tatsächlich.

Why do we use mich instead of the dative mir after informiert?

The verb informieren (to inform) requires a direct object in the accusative case. Since you are the person being directly informed, the pronoun ich changes to the accusative mich.