Help needed to submit my integration

Can anyone tell me how you prepare an integration for custom component / HACS integration?
I forked a custom integration and improved it. Spent days with Claude beating all the fancy requirements listed under the developers pages to make sure I had covered every base, tested it exhaustively with my hardware and did my first pull request. Only now do I realise that I thought I was writing an updated custom component, whereas the Home Assistant Developer Docs are all about core components. My efforts are now bogged down with a set of rejections from a bot and I'm pretty sure it will be rejected as too niche.
All clues gratefully received!

Did you consider creating a PR to the custom integration repository instead of creating a new one?
Or is the original custom integration abandonned?

I thought about that but my version is probably specific to a subset of Mertik controlled fireplaces with dual burners, so I suspect it is not a replacement for the existing version.