Since Qt 5.10, Qt does support both openssl 1.0 and openssl 1.1. This is a binary build time decision: Qt configured against OpenSSL 1.0 will not run with a system openssl 1.1, and vice versa.

The configure flag is however not considered when looking for openssl in the system paths: The logic is to always use the greatest version of libssl, libcrypto.

This has the consequence that, for distributions which allow you to install both variants in parallel, a Qt that is configured to compile against OpenSSL 1.0 will detect OpenSSL 1.1, try to load that, and fail.

Instead, the comparison in qsslsocket_openssl_symbols.cpp, LibGreaterThan should be changed to try to load libssl.so.1.0, libcrypto.so.1.0 first if Qt was configured without OpenSSL 1.1 support.