Add note about OpenSSL 3

Author: ltoenning

docs/home/system_requirements.md

@@ -36,6 +36,8 @@ Our *swift* applications have been designed to work on all relevant operating sy
     * glibc 2.31 or higher
     * glibcxx 3.4.28 or higher
     * OpenSSL 1.1
+    (OpenSSL 3 is **not** yet supported for official swift versions because Qt on Ubuntu 20.04 is built with OpenSSL 1.1.
+    Not installing OpenSSL 1.1 leads to warning messages like ``QSslSocket: cannot call unresolved function ...``)
     * libxcb-xinerama0
     * libspeexdsp
     * libopus