During the TLS handshake, is the server's TLS certificate sent encrypted? If sent in plaintext, it seems to me, the GFW could easily block connections based on the certificate, even if eSNI is used.

Based on this [1] description of the handshake, the DH random values are exchanged before the certs, so they could in principle encrypt the certs. But it doesn't say if this is actually been done.

[1] https://docs.microsoft.com/en-us/windows/win32/secauthn/tls-...