Doesn't it already do this? I keep a domain or two on HTTP to force network-level auth flows (which don't always fire correctly when hitting HTTPS) and I've gotten warnings from Chrome about those sites every time for years... Only if I've been to the site recently does the warning not show up.
Right now it only shows a little bubble in the URL bar saying "Not Secure", I think. (So, that is a "warning", in a sense.) TFA is saying there will now be an interstitial if you attempt an HTTP connection.
HSTS might also interact with this, but I'd expect an HSTS site to just cause Chrome to go for HTTPS (and then that connection would either succeed or fail).
> to force network-level auth flows (which don't always fire correctly when hitting HTTPS)
The whole point of HTTPS is basically that these shouldn't work, essentially. Vendors need to stop implementing weird network-level auths by MitM'ing the connection, and DHCP has an option to signal to someone joining a network that they need to go to a URL to do authentication. These MitM-ers are a scourge, and often cause a litany of poor behavior in applications…
I don’t believe Android IPv6 stack supports dhcp, so won’t be much use there.
IPv6 RAs also support prompting the client about captive portals similarly, too, I think.
(But also at some point that seems like a bug in Android.)
HTTPS url?
Chrome has shown the HTTP warning in Incognito mode for about a year, and has shown the warning if you're in Advanced Protection mode for about 2-3 years.