Downgrade to 2.9 till the porkbun plugin gets updated to work withb2.10.

I guess it depends on how you got caddy to begin with. If you used xcaddy, you have to update caddy the same way (recompile via xcaddy) otherwise you'll get the default binary which has no misc modules by default, which kinda sounds like what's happened but who knows for sure.

If you're feeling daring, you can try to compile caddy yourself with xcaddy, it's super easy.

Save your Caddyfile's (ultra important), and uninstall caddy. Install xcaddy (apt install xcaddy [or go install github.com/caddyserver/xcaddy/cmd/xcaddy@latest]). Then use xcaddy to compile caddy with the modules you need;

$ cd /tmp
$ xcaddy build --with github.com/caddy-dns/porkbun --with github.com/caddy-dns/cloudflare --with github.com/some-user/whatever-module

Caddy will build and be spit out in /tmp/caddy. Move it to /home/username/.local/bin or something, and make sure that directory is in your path. Don't forget to chmod +x caddy.

Run caddy like normal and see if this fixes your issue. If not, you'll likely have to try and older version of caddy (uninstall and specifically install the previous version or if you can't, use xcaddy with CADDY_VERSION to build a specific version with your modules), or wait until they push a fix for whatever they broke.

What are you using the porkbun dns module for, and how does it integrate with caddy? I think reverse proxy is not so related with DNS service, unless you are advertising caddy domains to porkbun via API.

Sorry, I don't use either of those services. Would you be willing to explain your setup? I use my own CA with HAProxy for TLS termination (with servers side TLS) so I might be able to give some general tips. Maybe.

I've never heard of Porkbun, but it doesn't sound like a caddy issue. Let's Encrypt requires being able to resolve the DNS name you're requesting a cert for, and to be able to connect to your web service and fetch a secret to prove you own the domain. If porkbun does something like punch a hole in your LAN firewall and let in http traffic, then porkbun is the problem. Not Caddy.