Would you know?
>I don't know how you could possibly be confident that your device isn't infected with something.
Easy, my bank account is still full.
How are you confident your phone isn't infected? Being up to date is no guarantee. Until you can poke around with root access to inspect everything it's still Schrodinger's cat in a black box you trust to not be dead inside.
Because how would malware ever make it into my phone? It doesn't just magic itself onto your device once it stops received updates. It needs an entry point off the attack surface. And what's my attack surface since all your examples don't apply to me?
I never download shady Apps from the likes of Huawei AppGallery lol or even off the PlayStore and I don't use Android 5. All apps I use are whatsapp and Google chrome, and I also don't browse shady websites on my phone.