Please provide an example package that fails. Clearly this is not a general
issue as everyday thousands of packages are installed

I had similar issue on clean installation 3.4 before, and fixed it in the same way as described by @jayss (create folder named 'packages' under folder 'administrator/manifests')

but I thought it something wrong with my hosting, so I was not very concerned for it
unfortunately I do not remember what the package I tried

The folder exists in core and releases:
https://github.com/joomla/joomla-cms/tree/staging/administrator/manifests

I wonder if it is related to #6180

@infograf768 but I think on clean installation Joomla do not install pkg_weblinks.xml so can be that why it fail ... just theory, currently I cannot confirm ... will need to try clear installation with latest RC build

Do you mean we have to include an index.html in the folder as we do for tmp and logs ?

Ah - that would make sense. The empty folder was created for me without a problem but as we already know there can be problems creating empty folders on some servers then it would make sense that we do add the index.html to this folder as well

Created a quick PR #6524 to add the index.html file to the manifests folder. This should therefore ensure that the manifests folder is always created

Closing as PR is merged.