Have you thought about using OpenBSD? You said that security is important to you, and OpenBSD is known for being secure. Their motto is “Only two remote holes in the default install, in a heck of a long time,” which shows how much they focus on security/hardening.
I made a guide for using sys-net OpenBSD. The guide needs some updates, but it works well for now. Just keep in mind that it it is advanced, so you’ll need to decide if you want to go ahead with it. You can install the OpenBSD template from @unman (thanks unman) to have a smoother experience, but I haven’t tested it yet.