Slackware Linux has still a steeper learning curve than most other distros. I use it since ... ever?

Distrowatch says: Slackware Linux is a highly technical, clean distribution, with only a very limited number of custom utilities. It uses a simple, text-based system installer and a comparatively primitive package management system that does not resolve software dependencies. As a result, Slackware is considered one of the cleanest and least buggy distributions available today - the lack of Slackware-specific enhancements reduces the likelihood of new bugs being introduced into the system. All configuration is done by editing text files. There is a saying in the Linux community that if you learn Red Hat, you'll know Red Hat, but if you learn Slackware, you'll know Linux. This is particularly true today when many other Linux distributions keep developing heavily customised products to meet the needs of less technical Linux users.