The instructions above are now out-of-date. Caddy V2 was first ported to the FreeBSD rc.d framework in August 2020. Caddy integration within the framework has since matured. That together with the caddy upgrade command introduced in Caddy 2.4.0 make it very easy today to keep Caddy up-to-date on FreeBSD and its derivates, such as FreeNAS.
References: