To install the Deep Security Agent on Ubuntu 20.04.5, follow the steps below:

1. Download the relevant DSA version for Ubuntu 20.04.5 and add kernel support on the DSM server. You can download the following supported kernel files: KernelSupport-Ubuntu_20.04-20.0.0-7733.x86_64.zip and KernelSupport-Ubuntu_18.04-20.0.0-7486.aarch64.zip.
2. Install the DSA package by running the following command in the terminal: sudo ./install.sh
3. Follow the on-screen instructions to complete the installation.

By following the above steps, the Deep Security Agent package can be installed on Ubuntu 20.04.5 successfully.

Note: The kernel support files mentioned above are required for installation. Ensure that you have downloaded the correct version of the kernel support file for your Ubuntu server.