Why do you need a "vendor" at all? Do the paperwork yourself and pay the $100 fee (or whatever it is in your chosen state), and Bob's yer uncle. At worst add in a one-time cost of $40 or so to buy a book like Nolo's LLC Handbook[1].
[1]: https://www.amazon.com/Nolos-LLC-Handbook-Agreements-Instruc...
You might want to use a registered agent rather than blasting someone's home address into all kinds of public records, or using an attorney who starts the billing clock to receive spam. And when you go for the more reasonably priced registered agents, it feels like a ticking clock until they start to enshittify.
Because you don't want to be your own registered agent.