Here is some up to date research demonstrating the effectiveness of masks in providing protection from Covid for yourself and others. www.pnas.org/content/118/49/e2110117118
That looks a really good paper.
But it looks to have quite small sample size — in skim read, it looks like the sample size might even be just seven individuals. Feels like that's probably wrong, but the number doesn't jump out.
It only seems to consider professionally manufactured masks, with no consideration of hand-made or even mass-produced non-surgical grade. It assumes that surgical masks are well-fitted, which is not a reasonable assumption.
Given that, while it's certainly a useful contribution, there is at best limited applicability to the topic of this thread.
I'd be very interested to see the results a variety of ill-fitted scenarios, along with a revised infection model based on what we know about Omnicron.