Why would you be running on dozens of distros on different architectures? With some sane level of standardization (lets say less than 6 combinations) it's easy

Why would you be running on dozens of distros on different architectures? With some sane level of standardization (lets say less than 6 combinations) it's easy enough to test all and fix up the discrepencies. The more declaritive you are, and the less you assume about the environment, the better this will work. Ie. if you need a package, always install it. On some distros it may be there by default, but you'll run into issues if it's not. The good thing about being declaritive is that there's no harm in checking.