I have many nerdy friends who have been Linux users for ages. But most of them don’t know such a thing as Openwrt exists or have never bothered to give it a try. It’s a very fun piece of software to play with and can be extremely useful for routing traffic. Wondering why it isn’t more popular/widely used.
That’s exactly what I do. You can keep your ISP router and hook up your openwrt router to one of its lan ports and have two wifi networks.