Given that the original thread was closed, I am going to continue the discussion here, and specifically with regard to this post by @Teo. 
The section about pacman-keys needs updating, because the packages referred to as examples still use the .xz filename suffix while Arch, Manjaro and other Arch derivatives have already long transitioned to .zst-compressed packages. And the reason why this is important is that we’ve just had a member tripping over that.
That member actually tripped more not reading
Use either your browser or curl to download. Using curl assumes you know the correct package name as located with the mirror. Replace YYYYMMDD-R as available from the mirror.
and copy pasting
curl -O https://mirror.easyname.at/manjaro/pool/overlay/manjaro-keyring-YYYYMMDD-R-any.pkg.tar.xz
which logically gave him a nice file manjaro-keyring-YYYYMMDD-R-any.pkg.tar.xz with the following content
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>404 Not Found</title>
</head><body>
<h1>Not Found</h1>
<p>The requested URL was not found on this server.</p>
<hr>
<address>Apache/2.4.59 (Debian) Server at mirror.easyname.at Port 443</address>
</body></html>
And of course he tried to install that 
But i do not know how much more clear can it be made, for those who do not want to read.
Yes, but it should still be updated in the Wiki that those are .zst packages, not .xz packages. That’s the part that caught my attention. 
The package extension has been updated.