There used to be several desktop blogging programs at the past, both commercial and free/open source, but they died because apparently putting everything in the browser is sexier or something.
Anyway, here is one i found out recently and seems to be able to do the job:
https://getpublii.com/
And a blog i made with it myself:
http://runtimeterror.com/devlog/
Having said that, the first thing a friend of mine (who has managed a few blogs professionally) asked when i mentioned it to him was "can you make posts from your mobile?". Of course the answer is "no" since this runs as a desktop application, manages everything locally and just generates HTML files that can optionally upload/sync to your server for you. But apparently every single non-technical client he had wanted to use their phone to write blog posts way more often than their computer.
And yes, i know this also explains the "because apparently putting everything in the browser is sexier or something" part i wrote at the top, but, dammit, i do not care about mobiles at all, do not go and kill stuff i (might) like.
(though TBH there are several things i dislike about Publii, e.g. the themes are both ugly and too overcomplicated to work with and modify and the program is written in Electron with for real benefit - it doesn't do real WYSIWYG, just a rich text editor almost with the same capabilities as the one you could find even in Visual Basic 4 and it doesn't even preview the site inside it but launches your browser instead, but there isn't really any other alternative that i know of and at the end it seems to work... though i'm itching to go and write my own :-P)