We discussed it a few months ago in another thread on how we needed a simple way for people to be able to generate their own SSL certificates so they could start better protecting their internal devices. Eventually I had found that tool, but lacked time to start diving into it. I only recently remembered it was sitting on my system, and started looking into it these past few days.
https://hohnstaedt.de/xca/index.php
This tool provides you with a GUI for all of your keys and certificate management needs. You can (relatively) easily use it to create your own Certificate Authority, and sign your own certificates with it. All you have to do is import your own CA root certificate on your computers at home, and then start emitting certificates for all your internal devices that support them (like most NAS, and Asus routers for instance). The beauty of it is that once you import that root certificate, any certificate you sign with it will be recognized as trustworthy by your browsers. No more security alerts. My own Asus RT-AC88U for instance now look like this in Chrome:
View attachment 12193
There's some learning curve involved however, especially if you're not familiar with how SSL certificates work. But tons of documentation on the web is available.
Ultimately, I believe the market still need a simpler way to manage it, for SSL neophytes. But if you're willing to start learning, or if you're already quite familiar with them, XCA can be a great tool to easily secure your internal devices without having to constantly click to accept untrusted self-signed certificates.