Is affordable, 24/7-reliable, electricity ever possible again?

In either case, downstream handling of hydrogen (compression, refrigeration, transport, distribution, etc) is complex and costly. Net energy delivered likely will be very negative. Time to deliver? Long at best. Beyond 2050? Ever?

Hydrogen is very flammable. It was when used for trans-Atlantic air travel. A Led Zeppelin?

'White' hydrogen? Naturally-occurring hydrogen has been found in various locations. Google it. In some locations, this might avoid the costs of electrolysis, however effected. But all the downstream problems of handling hydrogen noted above remain. Time to deliver? Long? As a widely available, grid-scale option, not likely.

Nuclear fusion here on Earth. This is a violent process conceptually akin to sustained tiny-H-bomb explosions. Extremely high, extremely concentrated, energy inputs are needed, preferably also in a very, very intense gravity well. Not available here on Earth? Workable in stars.

Research on terrestrial fusion has been going on for decades (eg, ITER since 1978). Including all energy inputs, little if any net energy has been produced so far, let alone at scale. Gravity-wise and temperature-wise, best supplied in the Sun's core and other stars. Unlikely on Earth?

Available in 30-50 years? Researchers have said so for decades. They still do today.

Nuclear fission here in Australia. Widely used. Relies on heat from slow radioactive decay. Long-lasting. Easily linked into current grid technology. Time to deliver? Relatively soon -especially compared with alternatives. Small Modular Reactors in future? Maybe.

Can low-emissions, long life, 24/7-reliable, lower-cost, electricity be delivered in Australia?

With renewables, I don't think so. Not by a very, very long shot.

'Firming' renewables at any scale needs fossil fuels today, not batteries. And at very high cost.

What's the known future alternative?

You be the judge.

On the evidence, of course.