I’ve been trying to up my use-package game recently and converted my hand rolled package check and installer to use-package. I usually prefer to use packages from melpa-stable so I pin the default package source used by use-package to melpa-stable and override it where necessary That’s working well in general and looks something like this:

(setq use-package-always-pin "melpa-stable")

(use-package js2-mode
  :ensure t
  :defer  t
  :custom
    (progn (js-indent-level 2)
           (js2-include-node-externs t)))

(use-package kotlin-mode
  :ensure t
  :pin melpa)

So in other words, if I’m on a machine that doesn’t have js2-mode and kotlin-mode installed, use-package will install js2-mode from melpa-stable and kotlin-mode from melpa. So far, so good.