Openssl 3 says these functions are deprecated and does not recommend using them. They also advise using the DH provided by openssl instead of the app providing it. 

https://www.openssl.org/docs/man3.0/man3/SSL_set_tmp_dh_callback.html

SSL_CTX_set_tmp_dh(SSL_CTX *ctx, DH *dh) is used in tls.c. What would be the proper way to fix it so that it is compatible with OpenSSL 3? Unfortunately I don't know if not using the DH provided by TLS would affect the behavior. The people at AS who were involved with the development and maintenance of this extension were already gone before I started.