Install urbackup client silently for example via group policy

how can i install urbackup client silently for example via group policy?

You can download the MSI file from the Downloads area of https://www.urbackup.org/downloads/Client/

Once you get it, create a group policy with the appropriate permissions, and add the file into the Computer Software Installation area, and update the group policy settings on the client.
May take a restart or two, but if everything is set right then it should just install the client onto the machine.

For reference of forcing group policy update on the machine:

gpupdate /force

However, I suggest trying without the force switch first:

gpupdate

you might want to refer to this post for silent deployment…

Or the easier method here: https://installercreator.urbackup.org/