Now you're talking about something completely different though. Connecting to a printer over LAN is not at all the same as a Web browser talking to a third party webserver over WAN.
Ie if you have a .dev domain that resolves to your intranet - you will still need HTTPS on example.dev, the browser won’t let you off?
Also, if this is really a problem, use a different TLD?
Split horizon DNS just how DNS works. Its weird that HSTS preload lists has made security decisions assuming all domains under these TLDs exclusively point to the internet, when that's not how DNS works
Just use another TLD is nice when everything is from scratch, but when it isn't it means migrating an intranet to another TLD and managing hostname changes for every instance under the domain...