Any good free antivirus for Android?

Can't see strict site isolation, under chrome://flags in my iPhone :cry:

You won't if it's like Chromium Edge, because it's native to the browser. Edge and probably Chrome now have a flag Strict-Origin-Isolation that strengthens site isolation.
 
I can't see the strict origin isolation flag either. Is there a reference pointing to this being on in a build-in fashion for iOS ?

I missed that you're using Chrome on iOS. All browsers on iOS use Apple's WebKit and these features (flags) aren't available.