@Erich_Gstrein, @steffen_KNIME I think there are currently some problems with Python based nodes and Proxies. They are not always working. There seem to be this workaround of creating a local collection of necessary packages in a KNIME version without a proxy and then transferring this. I have not tried it.
The zipped update packages are of no use. It would be great if the Python based nodes can use the Proxies set. I think I already initiated a ticket (which does not have a number as of yet it seems).
Also for some time now KNIME seems to struggle with recognizing which extensions are already installed and which are not. I have mainly seen this on Apple Silicon but with 5.1 it starts to show on Windows machines too.