DH_set0_pqg() has been available since LibreSSL version 2.7. This version
won't compile with opaque DH in LibreSSL 3.5.

Index: modules/crypt.cpp
--- modules/crypt.cpp.orig
+++ modules/crypt.cpp
@@ -68,7 +68,7 @@ class CCryptMod : public CModule {
     CString m_sPrivKey;
     CString m_sPubKey;
 
-#if OPENSSL_VERSION_NUMBER < 0X10100000L || defined(LIBRESSL_VERSION_NUMBER)
+#if OPENSSL_VERSION_NUMBER < 0X10100000L
     static int DH_set0_pqg(DH* dh, BIGNUM* p, BIGNUM* q, BIGNUM* g) {
         /* If the fields p and g in dh are nullptr, the corresponding input
          * parameters MUST be non-nullptr.  q may remain nullptr.