In German this term if often not translated.
In Germany in many fields of technology and engineering (not only computing) you use English terms without translating them.
When you translate the term into German many people will not understand.
If you use the word "Lootbox" most persons (being familiar with online games) will know what you are talking about.
If you are using any kind of translation no one will understand what you are talking about.
Is there a German "Loot Box"?
When talking about newly created words or foreign words I often read the question: "Is this a valid German word at all?"
The answer I nearly always read was: "If a lot of German native speakers understand this word then it is a valid German word; otherwise it is not."
Because there is no word or expression for "Lootbox" which is understood by many native speakers I would say that there is no valid German word which means "loot box".