I don't know anything about dev blogs, what they are supposed to talk about, etc...
But, I wrote one anyway once I released the game talking about the mechanics I didn't have time to add!
Edit: I'm don't write much, so it's probably not super interesting
https://bigghead.itch.io/lightsout/devlog/93286/my-gmtk-2019-submission-lights-out
And the game: