Development for LHC@home

On Linux the man page should be available once Podman is installed but you can also use a recent version from the web.

As for the containers.conf location on Windows I suggest to read the Podman tutorial here:
https://github.com/podman-container-tools/podman/blob/main/docs/tutorials/podman-for-windows.md
Based on that I suggest to put the proxy environment from my previous post in a file like containers\containers.conf.d\50-podman-proxy-environment.conf either below '%APPDATA%' or '%ProgramData%'.

... BOINC has to manage this by itself when the User has setup the Proxy-Info in the normal Client...

I disagree with this statement.
'http_proxy=xyz' is just an environment variable and Podman has a couple of well defined interfaces (containers.conf, special environment file, command line parameters) to pass arbitrary environment variables to a container.
So, there's no need to reinvent the wheel.
If you still want it to be solved by BOINC you would need to open an issue here:
https://github.com/BOINC/boinc/issues