The Masks4all paper (your link) is neither credible, nor is it a study. It should never have been published.

It is a mashup of a literature review with a bad methodology, and a simulation that adds no new information to the debate. It excludes and/or minimizes randomized clinical trial data when that data doesn't support the desired narrative.

For those who might read this later, the Cochrane collaboration published a high-quality review of masking literature:

https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD...