Rainbow

does anyone know how to use rainbowkit in browser environment? (umd/cdn/whatever)

Not directly supported, yet, unfortunately. I have in the past recommended using a bundler like Astro that allows you to bridge the gap between Vanilla JS and React. RainbowKit is ultimately a React library that relies on Wagmi React Hooks, so you'll need to bundle it. Alternatively, you can use wagmi/core connectors directly.

I did some more digging and I think it's just not possible

Mike is deferring to @danielsinclair 

but I would make a github discussion if he doesn't see this

he's also more online on X

https://github.com/rainbow-me/rainbowkit/discussions