LD_AUDIT is even more interesting, and lesser known. It will load even before preload, and has handy hooks for everything that the loader does. https://man7.org/linux/man-pages/man7/rtld-audit.7.html

And had some nasty easy to exploit privilege escalation problems a while ago, https://cve.mitre.org/cgi-bin/cvename.cgi?name=cve-2010-3847