Linux mint19.1There is antivirus for Linux, but it's usually not suggested since Linux usually isn't susceptible to viruses. You're likely to get several people replying telling you to not bother. Clamav is what is suggested if you really want AV on Linux. It should be available in your distros app repository. You can get it via the gui (possibly Synaptic) or by terminal with the command "sudo apt-get install clamav". I'm assuming by Linux 19.1, you mean Linux Mint 19.1. If I'm wrong and your distro doesn't use apt-get, replace that with the appropriate command.
Yeah that's where the old download url redirects to now, I contacted their support but they weren't able to answer why the free version download link is offline and being redirected. I am still able to retrieve updates so I'm not going to worry about it for now. Running the same free sophos antivirus on my vps running a mailserver. So will have to keep track on that just to be sure.
But if you need an AV for enterprise/paranoid usage, you can use:Seriously though, if you're smart enough to use Linux, then you're smart enough not to run random scripts.