Tx Masterzone,
that solved it. I got OSX 15.0.1, C4D 25.0.2 and the CR 13 latest daily build and Cosmos running.
I installed CR13 without Cosmos and updated Cosmos from within C4D/Cosmos and then ran the installer manually from the desktop.
Good to know it's an installer problem.
Anyhow, I am moving away from Cosmos as much as possible. Redshift had done a much better job with its assets within C4D. All Redshift assets are directly available though the C4D asset browser even though they are under subscription. I hope Chaos is going to put some more effort in Corona for C4D. I took a look at the roadmap but it seems we are at the end of it.