No-bullshit, essential newsletter platform?

I got lost in the Mailchimp UI 15 times. I don't need "enterprise-level features". I don't need a visual builder that creates an html monstrosity requiring a 6571x2536 resolution to be displayed properly. I don't need drag and dropping cows onto the screen. I don't need campaigns, 45 different signup forms, group breakdowns, and an analytics service that requires 2 PhDs.

I only need users to confirm their email, and me to send markdown emails. Any suggestions?

A good example is https://mataroa.blog/ , but I'm happy to keep owning my website as it is and avoid a migration.