This seems broken in both 3.x and 4.x: When opening the Marketplace via the reports instead of the admin settings (I'm still not sure if this duplication is helpful) the plugin search seems broken

It redirects to

https://matomo.dev/index.php?module=Marketplace&action=overview&embed=1&idSite=17&period=month&date=today&segment=&showtitle=1&random=3659&sort=

which is not a full page, but just an HTML widget.