No, you do not need an Antivirus (AV) on Ubuntu to keep it secure.

Is Anti Virus required for Ubuntu?

Do I need to install antivirus on Ubuntu? Ubuntu is a distribution, or variant, of the Linux operating system. You should deploy an antivirus for Ubuntu, as with any Linux OS, to maximize your security defenses against threats.

Do I need an antivirus for Linux?

Anti-virus software does exist for Linux, but you probably don’t need to use it. Viruses that affect Linux are still very rare. Some argue that this is because Linux is not as widely used as other operating systems, so no one writes viruses for it.