OpenSSL 3.0 is not yet released as GA, but we already experiment with the builds in Fedora (Copr repository available: https://copr.fedorainfracloud.org/coprs/saprasad/openssl-3.0/) or in CentOS Stream 9 (https://kojihub.stream.centos.org/koji/buildinfo?buildID=7571).
There are some documented changes in OpenSSL 3.0: https://wiki.openssl.org/index.php/OpenSSL_3.0 but there are also some changes that should not be visible. However, since other SW depends on some internals, the changes actually affect the compatibility more than documented.
MariaDB 10.5.9 (expecting 10.6.x behaves the same) fails to build with this upcoming OpenSSL 3.0.
The problem is mainly with md5, sha and crypto parts.
A partial fix is proposed here:
but some tests (related to encrypting) fail even with this patch, so it is definitely not complete.
MySQL report is https://bugs.mysql.com/bug.php?id=103818