Hello @runicar!
Another reason to use the smart phone just to call and send text messages 
It is truly regrettable that there are people dedicated to damaging systems and now smartphones. Which raises our level of paranoia. The strange thing is that these Trojans do not enter through the games.
Smart phone games are one of the most downloaded applications by people and I have generally been reluctant to "play" with the phone for the same reason.
There are antivirus applications, but they are always heavy and slow my phone down even more.
About handling crypto or bank accounts, I've never liked doing it on the phone, not only for the same paranoid reason, but also, because where I live in a matter of minutes someone could steal your smart phone if you wear it very visible.
Very informative your post
Keep in touch