What could software developers do for climate change?

Donate money to politicians who pledge to do something about it. And if you feel comfortable enough, (and if you earn enough, e.g. 400K+) attend donor events with both parties. Talk to senior politicians. Make it clear that the no 1 issue for you is climate change.

Literally just calmly persuade people on the benefits of nuclear energy.

Regardless of whether or not people are super-concerned about climate change, every viewpoint should be able to find something to like about this.

If you're scared of climate change, nuclear energy is the only feasible solution without cutting off power to the majority of the planet.

If you're not scared of climate change, you still want cheap and plentiful energy to power industry.

They can quit being software developers and become farmers instead

It is surprisingly cheap to buy out politicians.

We just need to crowd source them away from Industry/Oil&Gas interests.

This is way easier than political reform against lobbying/corruption/nepotism.

Find somewhere near you and get involved:

https://citizensclimatelobby.org/about-ccl/chapters/

Build an effective solution for remote work for developers. Then expand the solution to other employees that are not 'hands on' in a particular place. Something better than zoom and slack. Use multiple displays, cameras, speakers. The most environmentally friendly commute is no commute. The most environmentally friendly office building is no office building.

Well mining bitcoin is a good start… oh wait

Write everything in Rust :)