Given that has deduced svn process itself is stuck (not UE4 - that’s just waiting for process), would someone please try executing following command from command line (from within svn directory)?
svn status --verbose --show-updates --non-interactive --xml --trust-server-cert --username <user> --password <password>
If that doesn’t hang, there must be something special with way we are invoking process itself…
One other thing you can try is potentially using a more up-to-date system svn binary (if you have one), rather than one shipped with UE4. You can do this by adding following to your SourceControlSettings.ini:
[SubversionSourceControl.SubversionSourceControlSettings]
ExecutableLocation=/path/to/svn