I use Revue. It's free up to 200 readers. The default template is nice. You can link your Twitter, PH, Medium accounts to use content you already curated. You can publish on Medium at the same time. Love it.
If you really want super simple and stripped back, think no further than TinyLetter. It's like Simplenote, but for newsletters. I know people who have successfully built link-based newsletters on this.