Patch from Gentoo: https://gitweb.gentoo.org/repo/gentoo.git/plain/dev-qt/qtnetwork/files/qtnetwork-5.15.1-libressl.patch
--- src/network/ssl/qsslcertificate_openssl.cpp.orig	2020-09-02 10:15:07 UTC
+++ src/network/ssl/qsslcertificate_openssl.cpp
@@ -661,7 +661,7 @@ static QMultiMap<QByteArray, QString> _q_mapFromX509Na
         unsigned char *data = nullptr;
         int size = q_ASN1_STRING_to_UTF8(&data, q_X509_NAME_ENTRY_get_data(e));
         info.insert(name, QString::fromUtf8((char*)data, size));
-#if QT_CONFIG(opensslv11)
+#if QT_CONFIG(opensslv11) && !defined(LIBRESSL_VERSION_NUMBER)
         q_CRYPTO_free(data, nullptr, 0);
 #else
         q_CRYPTO_free(data);