/usr/lib/x86_64-linux-gnu/libmariadbclient_r.so is in libmariadbclient-dev 1:10.1.29-6.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libmariadbclient.so
/usr/lib/x86_64-linux-gnu/libmariadbclient.so