ldconfig behaving differently in /usr/lib and /usr/local/lib

I'm in an ubuntu 22.04 and have a binary that can't execute because it's missing libssl.so.10: ./nGeMTools ./nGeMTools: error while loading shared libraries: libssl.so.10: cannot open shared object file: No such file or directory So after downloading and locally compiling the lib I got the file libssl.so.1.0.0. I made a link to it in /usr/local/lib in the adequate name searched by the binary: /usr/local/lib$ sudo ln -s /usr/local/ssl/lib/libssl.so.1.0.0 libssl.so.10 /usr/local/lib$ ls -lah | grep ssl lrwxrwxrwx 1 root root 34 jun 18 12:14 libssl.so.10 -> /usr/local/ssl/lib/libssl.so.1.0.0 I also confirmed that /usr/local/lib would be searched by ldconfig because its mentioned in /etc/ld.so.conf.d/libc.conf: $ cat /etc/ld.so.conf.d/libc.conf # libc default configuration /usr/local/lib So I guess I don't need to create a new /etc/ld.so.conf.d/libssl.conf file with the same folder name in it. After running ldconfig, ldconfig -v weirdly returns, between other stuff: /sbin/ldconfig.real: Path `/usr/lib' given more than once (from :0 and :0) libssl.so.1.0.0 -> libssl.so.10 /sbin/ldconfig.real: /lib/x86_64-linux-gnu/ld-linux-x86-64.so.2 is the dynamic linker, ignoring Which seems to be the inverted link (what I want is libssl.so.10 poiting to libssl.so.1.0.0, not the other way around). Indeed, trying to execute my bynary returns the same error as before. However, if I do the exact same configuration in /usr/lib: /usr/local/lib$ sudo rm libssl.so.1* /usr/local/lib$ cd /usr/lib /usr/lib$ sudo ln -s /usr/local/ssl/lib/libssl.so.1.0.0 libssl.so.10 /usr/lib$ ls -lah | grep ssl lrwxrwxrwx 1 root root 34 jun 18 12:17 libssl.so.10 -> /usr/local/ssl/lib/libssl.so.1.0.0 drwxr-xr-x 3 root root 4,0K maj 16 08:32 ssl /usr/lib$ sudo ldconfig Then ldconfig -v returns, among other stuff: libssl3.so -> libssl3.so libssl.so.3 -> libssl.so.3 libxmlsec1-openssl.so.1 -> libxmlsec1-openssl.so.1.2.33 libssl.so.1.0.0 -> libssl.so.10 Which is still inverted... but now trying to run my binary returns: $ ./nGeMTools ./nGeMTools: error while loading shared libraries: libcrypto.so.10: cannot open shared object file: No such file or directory which indicates to me that it could load libssl and is now just missing libcrypto. Why is the behaviour different depending on the folders even if /usr/local/lib is on /etc/ld.so.conf.d/libc.conf?