It’s good for general computing, and if it’s off the internet it’s good for anything. But if it’s networked don’t trust it with things you’re not comfortable being at higher risk.

So watch YouTube fine, banking maybe not

The context here is a phone that’s no longer receiving hardware security updates, not lineage OS itself. If you put lineage on a modern phone getting updates, then I’d be comfortable using it as a standard phone doing all the standard things including online banking