What do you feel is cryptic about TOML? I always felt it was pretty straightforward, especially if you're coming from INI (you could feed INI files into a TOML parser and most of the time end up with something somewhat sane, especially if you're using octothorpes instead of semicolons as comments).
That aside, I'm personally a big fan of using Tcl-like / shell-like syntax for configuration, since it enables some pretty rich and expressive config directives while not being insanely verbose like most attempts at using XML for this. It's one of the things I really like with OpenBSD's various subprojects like PF¹ and OpenSMTPD² and relayd/httpd³, and I'm semi-actively working on a way to do similar things in Erlang/OTP applications⁴. The only alternative that matches that level of expressiveness (besides just doing all configuration directly in the host language) is s-expressions.
¹: https://man.openbsd.org/pf.conf
²: https://man.openbsd.org/smtpd.conf
³: https://man.openbsd.org/relayd.conf.5 / https://man.openbsd.org/httpd.conf.5