> Unfortunately, hardly any tutorials pointed this out and used their own CA for everything instead.

I think this is one of the reasons so few people consider using TLS auth. There aren't many guides out there, and many of the ones that are easily accessible use a custom CA deployment that's an absolute pain to manage (custom TLS certs on websites with a custom ACME server or manual certificate generation, and so on).

Sometimes I feel like writing my own guide, but I'm not 100% confident that I'd get everything right.