In the Linux world, I'd go with Alpine or Void, and OpenBSD for non-Linux adventures.

OpenBSD is certainly way simpler than Linux. They focus on security, but it often also results in simpler code as a side effect. But even without the security stuff, they try to keep things simple.

That comes with a price, of course: Linux has much more features than OpenBSD and much better hardware support. This may or may not be an issue for you.