My guess is that is the opengraph[0] crawler for Substack Notes[1], the Twitter-ish alternative that Substack is making, so like someone posting a link to your blog, it visits, grabs meta tags to display a link preview.
Edit: I was indeed correct, I went on Substack notes and wrote my own site, but the bad part is that it crawls as you type your post out, so instead of 1 request it'll be several!
[0]: https://ogp.me/
[1]: https://substack.com/notes
Edit: I was indeed correct, I went on Substack notes and wrote my own site, but the bad part is that it crawls as you type your post out, so instead of 1 request it'll be several!
> Sun Apr 30 2023 23:56:03 GMT+0000 (Coordinated Universal Time)]: | Ip=34.200.242.86 | Req_page=/?substack_notes | Agent=SubstackContentFetch/1.0 (https://substack.com/)