How to use the Unleash Edge proxy?

Question

I have a running setup with an Unleash SaaS instance and an Unleash Proxy. I have a backend that connects directly to https://eu.app.unleash-hosted.com/eu.../api and React SDK client that connects to the proxy. The Proxy run on my infrastructure (unleashorg/unleash-proxy:1.2.1) and SDK connects to it with

UnleashClient({
        url: `${ document.location.origin }/proxy`,
        clientKey: '...',
        appName: '...',
        ...
})

I would like to use the Edge Proxy because I need offline mode for a new Deployment. I'm stubling over the following:

1. https://docs.getunleash.io/reference/unleash-edge mentions that there're connection instructions how to connect the SDKs on their READMEs, but there's none
2. There's a migration guide from Proxy to Edge https://github.com/Unleash/unleash-edge/blob/main/docs/migration-guide.md which requires very detailed knowledge about what you're using currently, since there's tokens, client tokens, frontend tokens and client keys. I assume they trigger different connection modes (that the best theory I've come up with so far in order to make any sense of the instructions). I tried all of them with trial and error without success.
3. There's no information who the connection URL looks like, without this information I won't be able to make a connection. There's inconsistent use of /api, /api/frontend, /proxy in the docs based on the infamous {unleashUrl} that I've seen all day. I assumed that it's the host without any path and conducted all my trial and error experiments with it, without any success. So now I assume that it's not.
4. There're no examples how to setup the Edge Proxy, the whole docs are based on assumptions that I cannot make, like "if you want to use client tokens, do this" (I don't know what client tokens are and didn't manage to find out after the whole day reverse engineering docs).

So far, I'm only getting a 405 Method Not Allowed from the Unleash Edge instance I'm running locally.

The only "support" that Unleash provides is a link to their internal Unleash Slack which I cannot access because it's internal.