Any good free antivirus for Android?

Most smartphone comes with a basic scanner so adding one is not necessary, just don't install crap apps and check their permissions.

But if you really need one, i vote for either Avast or Sophos , i prefer Sophos because less bloat and ads.
 
Every app is sandboxed in Android and Chrome mobile uses strict site isolation and sandboxing for each tab as well. The most important thing is to have the latest security patch, a relatively modern phone from a company with a good reputation and use brain.exe. An app called "Super Antivirus Free VPN" should be treated with a grain of salt. If you stick to the popular apps, you will never run into malware. Never had Android malware in my life.

I highly recommend getting a phone that doesn't come with questionable bloatware pre-installed and preferably Android 9 or higher because it has stricter permissions. I'm on Android 10 and the permission system is brutal. Never seen something like this in an OS. Android 10 is extremely strict with everything especially clipboard.
 
I just installed Sophos again after not using it for awhile. It has changed the way you configure it so you can use only the modules you wish. It took a bit of figuring out but I think I like this new version more than the last. I've enabled Scanner, Web filtering and Wifi security. (y) (y)
 
I'm gonna second for Sophos, if it's free. Also check what @Umbra mentioned. For example, my Samsung Galaxy S8+ brings automated optimizing tools, a cleaner powered by 360 and a malware scanner powered by McAfee. Usually this tends to be enough. Else, Sophos provides everything a paid app offers, plus totally free and no ads or compromising privacy.
 
I'm gonna second for Sophos, if it's free. Also check what @Umbra mentioned. For example, my Samsung Galaxy S8+ brings automated optimizing tools, a cleaner powered by 360 and a malware scanner powered by McAfee. Usually this tends to be enough. Else, Sophos provides everything a paid app offers, plus totally free and no ads or compromising privacy.

My phone came with McAfee and I used it with the other free tools like your post but M started to give me premium nag, otherwise I would have kept it.