@firstname.lastname@example.org in short, yes, it is a thing!
Lots of great replies to your post already about directly using #WithKnown or #WordPress with the #ActivityPub plugin, or cross-posting from/via GitHub.
Another #IndieWeb compatible option is Bridgy Fed (https://fed.brid.gy/) which can proxy posts, replies, likes etc. directly from a blog to #fediverse / ActivityPub (no #Mastodon account needed). Details: https://fed.brid.gy/docs
This very reply to your toot is from my own domain, and its #hashtags are also discoverable via fediverse hashtags.
I set up #BridgyFed last October¹ along with the broader #TwitterMigration I saw happening in my circles, and am quite happy with it. Posted more about my experience after a few months², and using BridgyFed to add a fediverse follow form to my homepage³.
Whether WordPress, Known, or with another blog setup & Bridgy Fed, pick what works best for you and your setup. There’s #IndieWeb folks using each, feel free to drop by https://chat.indieweb.org/dev to chat more about any IndieWeb/fediverse option!