On Ubuntu you have Apparmor, and mandatory access control (in practice, any sandboxing mechanism) is vastly superior to antivirus, at least in default-deny mode

On Ubuntu you have Apparmor, and mandatory access control (in practice, any sandboxing mechanism) is vastly superior to antivirus, at least in default-deny mode (which, sadly, Ubuntu does not use by default). If arbitrary software needs administrator level policy set to access the filesystem or devices, rogue software cannot harm your system. If trusted packages also need policy, then exploits in that software cannot do any more damage than the minimum amount of capabilities allocated to the application, which is quite frequently just the apps config file.