My particular approach was to start a company (Watershed[0]), but today there are lots of great options as a software engineer. There are already plenty of great examples in the thread of places to look for companies (MyClimateJourney community, climate job boards, etc). I think the most important thing is not to feel like you need to learn a ton before jumping into the fray. Most engineers that joined us had zero climate experience beforehand. All you need is to be curious, be an effective engineer and you can learn what you need on the job.
My email is in my profile if you want to chat!
[0] We’re hiring (https://watershed.com/jobs) and engineering is absolutely our rate limiter in helping companies decarbonize. We’ve built a climate platform that’s powering the climate programs of some of the world’s leading companies (Block, Shopify, Doordash as a few examples). Our goal is to be responsible for reducing the world’s yearly carbon emissions by 500 megatonnes of carbon by 2030 (1% of global emissions).