I’ve been using Tailscale because I like the business model they’ve been pushing. They’ve also followed through with that, expanding what the free tier of their service offers instead of restricting it more.
Although possibly biased, Tailscale has a write up comparing the two and the conclusion is that both are good at accomplishing their goals. If you have a technology or business preference, it could mostly come down to that. https://tailscale.com/compare/zerotier/
That's a very narrow definition of self hosting. Do you also not consider it self hosting if you use a cloud provider VPS? It relies on a 3rd party so I'd love to see the gymnastics that keep stuff on a VPS as self hosted but not Plex. If you don't consider things on a VPS as self hosted then I'm not sure what to say other than I disagree.
The identity service is not self hosted then. But the rest of Plex literally is. You can self host Gitea and use a third party service like openID for authentication too if you want to. Just because you self host some things doesn’t mean you HAVE to self host EVERYTHING
The original question was about the use of these two services. I answered their question and provided a link. I’m sorry that you took that as advertising, but the OP was asking for the basics. There are more productive ways of responding than immediately attacking, though, that would have helped get your point across. For example, providing links to things like Headscale or Netmaker to help your point about not using a third party service.
Also a big fan of Tailscale. Works well out of the box and they have great documentation.
I'll also throw out its nice to see many of their articles comparing services don't end with a simple "We're better!" but a "pick whats best for your use case." Makes them look a lot better imo.