There are plenty of electrical high heat technologies available already. Mostly companies have stuck with gas mainly because it's cheap and avoided exploring alternatives for quite long for that reason.

But there's plasma heating, arc furnaces, induction heating, infrared, resistive heating, heat pumps, etc. You can cover anything from thousands of degrees to (more commonly) hundreds of degree with these. Some steel plants already use arc furnaces or induction heating to melt the steel.

I'm not sure where this technology sits but it all boils down to cost and effectiveness. If it works as advertised, companies will use it.

The thing with green hydrogen is that you need even more electricity to generate it. Which makes some of these alternatives more economical because you can use the electricity directly at a higher efficiency.