What does that mean exactly? The latest version is v2.3.0, and the difference is quite significant.
This doesn’t look like a valid Caddyfile. What’s some_ip? The syntax for root is incorrect (needs a * as the first argument for the path to not be considered a matcher). Having the / at the end of your site block will only accept requests for exactly / and nothing else in v2, because path matching is exact (so remove that trailing /). And log stdout is not valid in Caddy v2.
All that said, I’m not yet aware of any rate limiting plugins for Caddy v2. You might use fail2ban though, you can find a recent thread about that (but it’s not so simple)