For reference, here is one for Nuxt3 (I'm completely unaffiliated):

https://supersaas.dev/

I've had many projects in the past be bogged down by implementing routine things again and again, so the idea of paying for one is appealing, but I was curious if anyone in Hacker News has successfully built a product from such a starter project?

It equally seems like it could be entrapping to work with someone else's code for something so important in a project.