That’s great! I definitely understand your concern. Diversifying your writing channels is never necessarily a bad thing, and it might be that LinkedIn is indeed more well-suited for your niche than Medium is.
One of the positive aspects of writing elsewhere is it could strengthen your case to publication editors regarding why they should choose your content over someone else’s (by validating your determination and quality of work, even if it isn’t on Medium).
For the amount of followers you have, the engagement you’ve received on your articles is actually very impressive. Perhaps, when you send your work to a publication editor, you could leverage that piece. By highlighting how you’re technically writing engaged content, and the only thing you’re missing is scale (which the publication can provide to you), you may be able to catch the attention of editors.
Lastly, be sure to try out the smaller publications too! By hopping on the small to mid-tier publications now, you’ll benefit in the long run :) Hope this helped, and hope to hear from you soon as to whether or not this worked for you.