A 2023 Cochrane review of 78 RCTs found:

The pooled results of RCTs did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks. 

There were no clear differences between the use of medical/surgical masks compared with N95/P2 respirators in healthcare workers when used in routine care to reduce respiratory viral infection.

Scientific American refuted, with this:

Placing randomized trials above other types of research such as observational, lab and modeling studies, has interfered with the COVID response. A randomized trial approach that allows a few studies [78 is not a few?] to cancel out a huge body of research from other disciplines has no basis in science.

Other small notes: 
- succinct general write up; 
- disagreement within Cochrane about what their review means.

+ How effective are mask mandates? 

+ How effective are N95s (when used correctly)? 
If they are effective, why do mandates seem to have done about nothing at all? - Or are these 78 RCTs not good evidence?

+ Why is it difficult for an ordinary person to figure this out, 3 years and a massive global effort later?