Backup your data so that you can restore what matters to you. There is no need for an antivirus on Linux if you stick to the distribution channels of your distribution because package are verified. Unlike in the close source world because the source of those packages are open, verifying, even though imperfect, is much simpler. Popular distributions, e.g. Debian or Redhat, have a very strong incentive not to let anything slip. Maintainer of packages also are able not just to track what changed but also by whom, that means if there is a problem it can be identified and attributed rather quickly and thus other maintainers can be warned. It is not impossible and supply chain attacks do happen, e.g. xz backdoor, but it is rare, specific and has been studied and thus partly alleviated even though it remains a challenge.

If you do download executables or binaries, not media e.g. videos or music, from random places though then all bets are off.