I wish Caddy would support brotil, is either gzip or zstd currently.
The thinking seems to be due to how CPU intensive it is, Brotil is not favoured for on-the-fly compression[2].
If you're really desperate for it though, you could try [this extension][3].
[1] https://caddyserver.com/docs/caddyfile/directives/file_serve...
Other webservers support it, mainly Nginx. But since Caddy is written in go, they need a native go port which doesn't exist yet.
Yeah, hence my "really desperate" qualifier. I probably should have been more explicit.