[semi-extrinsic]

ArXiv has email search alerts. I subscribe to a few topics, they are well formatted plain text digests.

I also have a few ScienceDirect search alerts set up, that come in once every few weeks typically with 1-5 papers.

And Google Scholar, if you use it and you are logged in with an account, learns from your search history and suggests new papers for you to read. It's relatively good.