As a self-appointed #PlainText advocate and penny pincher, it's significant that I subscribe to Setapp, and have done for more than 2 years.
My most recent article discusses 6 plain text friendly Setapp apps and utilities that can help you polish, protect, and present your text:
@markmcelroy @ellane The biggest downside to me is that if you stop subscribing to #SetApp (or there’s a processing glitch with your payment), all the apps completely stop working. That’s okay for utilities but a dealbreaker for productivity apps. (Iirc, with the direct subscription to Ulysses, at least you can open and export the work you’ve already created, even though you can’t work on it further.) There’s also a separate SetApp subscription to pay if you want the iOS versions of the apps.