How to load a local package - a directory somewhere with a bunch of .el files?

[monkeyjunglejuice]

The howto/readm describes tons of special cases involving complex setups, but I couldn't find any straightforward example how to write a recipe of a folder with a Git repository with some Emacs Lisp files in it.

Could you include this in the readme at a prominent place? Or are local packages/repos/folders out of scope?

[raxod502]

Just (straight-use-package mypackage :repo "/path/to/package") should do. It can be added to the documentation.