Does anyone have any idea on how I could evade my cell provider's block on 4chan?

For context, this is not a DNS-level block but a proxy in the middle that intercepts unencrypted connections, and sends a block page if any Host header matching *.4chan.org is sent.

What I don't understand is how they're doing this to encrypted traffic too. If I test with a curl -vv https://sys.4chan.org then the TLS handshake fails:

* Connected to sys.4chan.org (104.19.142.99) port 443
* TLSv1.3 (IN), TLS alert, access denied (561):
* OpenSSL/3.2.1: error:0A000419:SSL routines::tlsv1 alert access denied

I can connect to other sites using the same Cloudflare IP just fine. So they must be somehow detecting that this is traffic to 4chan, despite the connection being encrypted.