For me it doesn't show on desktop firefox(latest) and mobile brave(latest) on two different networks... I'll try my desktop firefox at home later, but bottom line it's accessible if you just click it from the side panel and go directly to its page.
For some reason, I cannot install it. It does not error out, and seems to do *something* for a fair while, then the MSI screen silently vanishes and it is not added to Installed Updates. The last .NET4.8 package still installed successfully. Yes, the Bypass for .NET4 is enabled.
Did you check if the files are updated (sort by Date modified) in "C:\Windows\Microsoft.NET\Framework\v4.0.30319"? the update has no registration info, it does not show in Installed Updates
This means that KB5101006 has been already installed on Your system. Because there is no registration info in latest update the only way to verify if it is installed correctly is by checking date timestamps of installed files 2026-06-03 (newest file ServiceMonikerSupport.dll) indicates that the current update KB5101006 was successfully installed.