Looking for alternatives to auth0 and clerk (user login services)

Wondering if people can recommend some alternatives to Auth0 and clerk.dev.

I have an existing site that is as vanilla as you can get (server rendered pages with Hapi.js and JS client features written in regular old javascript. No frameworks are used like React, Vue, etc.

I have some simple requirements where I want to add user logins so I can build some further features around that.

I can role that out on my own easily enough, but dealing with security issues and maintaining all of the issues that come with home-rolling a login system isn't something I want to do.

So, I've tried both Auth0 and clerk.dev over the last 2 days. For various reasons, I haven't been able to get either of these to work. Even exactly following Auth0's quick start guides leads to authentication errors with no clear answers why. (Google's results are un-surprisingly poor as usual.) And there's lots of commentary out there about how using Auth0 is an overall negative experience in the long run.

I monkeyed with clerk.dev for a few hours today and immediately found a couple of bugs I reported. And despite their documentation, it seems their UI components are React-only even when using their JS sdk.

I'm probably doing something wrong somewhere, but at this point I'm 2 days past where I wanted to be on this project. All I want is a simple to use drop-in login/user management system. Nothing dependent on this framework or that one.

Any recommendations?