The current sentiment among developers is content ownership. By posting on dev.to, you are giving away your content for free. If tomorrow they shut down or paywall your content (like Medium), you have no other option. On the other hand, Hashnode offers something called Devblog (hashnode.com/devblog) using which you can host your blog on your domain and truly own your data. Plus you get the other benefits of Hashnode. So, the correct approach IMO is to publish your blog posts on your own domain first (using Hashnode's devblog) and then republish them on other platforms. This way you retain control of SEO and truly own your content while getting benefits and exposure of other platforms.
You can read this related thread: hashnode.com/post/devto-or-hashnode-cjvrpqr240034…
Never give away your content for free!!!