This problem has been brought up in the OpenZiti community many times. I like Nebula, but it's not 'truly open source'.
I made a shell script that does most of that for my needs.
Edit, since I can't reply sadly:
You're right, that was a bad example.
I can probably list at least a few dozen things that all require certificates though, which was really my point. Everything has dependencies.
Also if you just... Don't trust big tech, run your own CA.