I wouldn’t recommend using anti-virus software. It usually creates a lot more overhead, plus it usually mimics existing solutions already in linux. The only viruses I have ever caught using an anti-virus software on Linux are the test viruses to see if all is working fine.

Anyway, here’s my 20+ enterprise experience recommendations with Linux :

• enable secure boot: will disable launching non-signed kernel modules (prevent root kits)
• enable firewall: and only allow ports you really need.
• SELinux: it is getting better, and it will prevent processes to access resources out of their scope. It can be problematic if you don’t know it (and it is complex to understand). But if it doesn’t hinder you, don’t touch it. I do not know AppArmor, but it is supposed to be similar.
• disable root over ssh: or only allow ssh keys, or disable ssh altogether if you do not need it.
• avoid using root: make sure you have a personal account set up with sudo rights to root WITH password.
• only use trusted software: package managers like apt and rpm tend to have built in functionality to check the state and status of your installed software. Use trusted software repositories only. Often recommended by the distro maintainers. Stay away from use this script scripts unless you can read them and determine if they’re the real thing.

Adhering to these principles will get you a long way!

edit: added section about software sources courtesy of @dragnucs@lemmy.ml