Is there any antivirus installed by default on any popular linux distro?

no.

What do you use?

uBlock Origin.

you don't need antivirus with linux.

there are next to no linux viruses. there is a bit of malware, but mostly targeted at servers. just don't excessively download and execute random stuff. and don't type things like "rm -rf /" into your console, if people tell you to. use your package manager where you can.

(most linux antivirus is used in like email-servers to scan mail before sending them out, so the windows clients don't get infected. antivirus on linux is seldomly/never(?) used to protect the linux itself.)

If you are on Windows, you already have a good antivirus program built in, and that is Windows Defender. Other than that, be sure to install uBlock Origin extension in your preferred browser - it not only eliminates ads, but also annoying pop-ups, embeds, trackers, malware sites and other annoying things on the internet. When you want to download something, and you're not sure if it's safe, scan the download link with VirusTotal.

No.

Just have backups of your data. If i get infected, I wipe and nuke from orbit anyway, I don't trust that antivirus will remove everything.

Windows defender has significant protections in place, it's quite good.

Windows defender is more than enough. On Linux, you don't need one, but there's clamAV, which scan for windows viruses.

In my experience the most effective antivirus is common sense

Contrary to other's recommendations I'm gonna say that it isn't a bad thing to run an AV on your files. Even if it's not going to affect you, you might not want to arbor virii in your library. ClamAV is the main anti-virus for Linux.

My paranoid me has no concerns in regards to Linux but I am running pyload in an LXC under proxmox to download you know what for my Windows PC.

So before using the files I would like to have them checked.

Therefore I just finished my setup.

Debian 12 LXC unprivileged, running pyload through openvpn tunnel. clamav does daily checks in the download directory and sends me an email if anything is found.

I would say for Linux to ust use uBO+FF and to not blindly copy terminal commands from the internet or to run random files with root. As many other comments have said there's clamAV to scan for Windows viruses but since Linux is far less prone to viruses (due to Linux viruses being quite uncommon), I think you're good without one.

Thx all. Im using ublock and im not clicking random download links, but Ill check virustotal and clamav Cheers

I don't bother but I do run an online scanner every now and again such as eset antivirus or malwarebytes if I'm feeling paranoid.

I'd also try to memorise every file in my startup but I used to write trojans, password crackers, and other dodgy programs myself when I was teaching myself how to program.

Personally I never went further than dll injection so I might be living in the past. The last virus to wreck one of my systems was pespaces 95 way back in the 95/98 days

I'd say memorising your startup or at least screenshooting it is key.

In my opinion windows defender is worse than not using an antivirus at all because of the false sense of security. I'm sure that the guy who got his Bitcoin stolen from downloading fake OBS software has windows defender enabled like everybody else.

I'm not suggesting you go out of your way to disable defender, but exercise common sense and good security practices instead of relying on any antivirus. Download software from package managers (winget, scoop, chocolatey) instead of from Google and always read the megathread for getting "other stuff". Install an adblocker on your browser and block as much 3rd party and Javashit as is practical. Don't use the administrator account as your main account. Sandbox your programs if you're feeling extra paranoid. Always back up everything important somewhere else. Use TRON script (r/tronscript) to clean up your computer in case you get infected.

However always keep in mind no strategy is 100% safe, but a little common sense goes a long way.

I don't bother but I do run an online scanner every now and again such as eset antivirus or malwarebytes if I'm feeling paranoid.

I'd also try to memorise every file in my startup but I used to write trojans, password crackers, and other dodgy programs myself when I was teaching myself how to program.

Personally I never went further than dll injection so I might be living in the past. The last virus to wreck one of my systems was pespace way back in the 95 days

I'd say memorising your startup or at least screenshooting it is key.