Sibling commenters are correct, I think a static site generators are the gold standard, since you'll be able to curate the feed to the way you usually post. Judging by your interest in aggregating, it seems Gatsby may be a fit:
Gatsby allows aggregating sources, e.g. https://www.gatsbyjs.com/plugins/gatsby-source-twitter/, https://www.gatsbyjs.com/plugins/gatsby-source-instagram/, https://www.gatsbyjs.com/plugins/gatsby-source-medium/
From scratch, I created a CV that aggregates all my GitHub stuff and hard codes the rest:
v1: https://cv.git-pull.com, https://github.com/tony/cv/tree/v1/react
v2: https://cv-react-v2.git-pull.com, https://github.com/tony/cv
https://www.instagram.com/successbykim/
...links to...
Is there anything off the shelf that I could use today?
What you are asking for is something like allyourprofiles.com/gajus where you can put all your online profile links... but why do you need the indirection? Just use one of your already existing social media profiles and use it as your "entry point": from there provide a link to all your other profiles. Easy.