I like Caddy, it's been great, but I have no interest in paying for support, and I'm certainly not going to pay to remove a HTTP header.
Yes, I could spend time setting everything up to build custom versions of Caddy without the header, but it'll be quicker and easier to switch to NGINX.
Whilst I really appreciate all the work that has gone into Caddy, I am extremely annoyed that it's now going to cost me at least an afternoon to move away from.
If you're an existing Caddy user and don't want to (or can't) pay, your options are either don't upgrade, server ads for Caddys sponsors, or spend a significant amount of time configuring your own build process/switching to something else.
I can't help but feel this move is going to be bad for Caddys adoption.