yes, it is 或者是.
From the meaning, 或 alone is alright here. 或者 and 或 means the same in Chinese.
Sometimes the choice between 或者 and 或 is related to the rhythm of sentence.
然後讓更多的德國人[pause here]或者是歐洲人[pause here]認識這個琵琶。
Both 更多的德國人 and 或者是歐洲人 are with six characters/syllables.
Another reason is a historical one. 或者 is commonly used in Classical Chinese as the start of a short sentence (complete or incomplete in English sense). 「或者是歐洲人」is treated as a short sentence.
If you want to dig a little bit deeper about 者, here is my explanation.
者 can accept anything before it, any word, any phrase. It is a marker referring to anything prepended to it. You might perceive it as "one that". 或者 is "one that is alternative" or "alternative one" and it simply means "or".