While it is well documented that the Vikings did engage in trade with the Islamic World (such as spices and slaves), I think it is a little farfetched to claim that they adopted significant aspects of Islamic culture and ideas.
First, the burial shroud lacks the ‘shadda’, ‘daggar alif’, and ‘ha’ strokes that you find in the word Allah. I think that this researcher may be misinterpreting her findings. Have you heard of a Rorschach test? This is the same thing in that people see different things depending on their perception.
Second, even if we accept this artifact at face value, it seems rather out of place. Are there any other artifacts that suggest contact with the Islamic World within its vicinity? How about within the same historical period? Can the cultural influence of Islam be demonstrated in other historical records such as Viking texts? When doing excavation, archaeologists usually try to place an artifact in a given time period and want to understand the historical context of an artifact. Why might there be a burial costume with an inscription of Allah on it? If the Vikings really did adopt Islamic religious and cultural beliefs, when was this and why did it happen? It is not good archaeology if we divorce an artifact from its historical context.
Also, if this really is an innovative finding, why has it not been addressed by scholars and expert in the study of Vikings? Surely this finding, if it is true would not be kept secret from the scholars and from the public? I recommend that you look at archaeologists such as Jason Colavito, Kenneth Feder. These are some great professional archaeologists that you should look into reading.
I think that there is actually a political motivation behind this, Dr. Larsson and her fellow researchers may want to make Europe seem like a more culturally diverse place. This stand is far different in comparison with how White Nationalists really love the Vikings. While this may be an honorable goal, it doesn’t justify bad archaeology.
Overall, I’m not convinced that this burial costume displays the word Allah; and I don’t think that there is any evidence that Islam had a profound impact on the cultural beliefs of the Vikings.
I hope that you continue finding new information and be sure to think with a critical eye.