If you can get a good job writing closed source software that gives you a decent quality of life and gives you the free-time to contribute to some open source projects outside of work I think you'll still do good for FOSS. Don't let perfect be the enemy of the good.

At the end of the day we have to be realistic with ourselves about the world we find ourselves in and the limits of the power of an individual in it. Starving for the sake of some imagined purity or living a lower quality of life isn't Marxist. As long as you're not directly abetting the imperialism machine by working for some ghoulish NATO defense contractor I don't think you have that much to feel badly about.

That said there's things like programming around helping coordinate mass transit and provide info to travelers. Programming for industrial machinery including especially in areas not related to manufacturing of goods like power, utilities, and though that's pretty specialized if you can get your foot in the door you have a fairly interesting skill-set. Government jobs for government agencies are also an option.

There are companies that write open source software that isn't free to companies (e.g. they charge for use when used as part of a profitable enterprise or sell support packages to large enterprises) but they aren't that great in number and to get in the door you've a better chance if you have something on your resume already which means unfortunately working for a for-profit, usually closed source company.

Hypocrisy is good and well for the idealist to worry about. The realist however cares more about feeding the children, feeding themselves and doing what they can with what they have. There is in the FOSS movement a certain idealism among many that think via free computing they can free humanity when in reality you must via revolution free humanity to free computing. FOSS is a rebel insurrection against capitalism but not one that can ever change the superstructure or base in any meaningful way on their own.

Never forget under capital you are forced under duress to sell your labor, it is not your fault, you are not a bad person for doing so and for doing so under conditions less than ideal for people who uphold a way of doing things you find philosophically repugnant.

So try, try to find something that fits these ideals but if you cannot, do not feel too badly.

I work for a company that writes software electric and gas’s utility companies use to coordinate power hungry iot devices like thermostats and evs to make power consumption less spikey and more predictable , which lets them supply demand more with solar and wind as opposed to coal peaker plants.

The utility gets a massive savings when peak demand of electricity and gas is controlled more, and pay our company as well as pass a portion of the savings directly to the device owner as a rebate on their utility bill (device owners sign a contract to let utilities manage their devices through us, but every control event has an opt out option so that the device owner can choose not to participate, but the less they opt out the more money they save on the utility bill)

capitalism will make it impossible for me to exercise my profession in a good way, but is there no alternative that fits in the middle anywhere?

One possibility is to find organizations that you like and do IT work for them. Especially for budget conscious lefty groups or nonprofits, they would very likely appreciate any FOSS software recommendations.

There's a lot of work to be had doing maintenance and training in FOSS software rather than developing. It's not as glamorous, but it's of equal if not greater importance, since those using FOSS often need it due to low budgets (and therefore can't always expect highly trained employees).

But the bad news is that your bio says you're Brazilian, and the FOSS scene has been really bad in Brazil since Temer. Government has cut a lot of investment in developing national open source software, and even critical government bodies like the Receita Federal (IRS-equivalent for english-speakers) are now back to being fully reliant on windows licenses.

I've even heard that national banks want to migrate their ATM systems and networks to Microsoft systems, and they use shitty software like Teams for """security reasons""".

We're in a bad state, but if you want to work on FOSS, you should try to think small. Social Assistance centres, small firms, maybe even research, that sort of thing.

But in the end, free software is free infrastructure, so don't be surprised when you see big techs funding what's supposed to be their antithesis if it marginally reduces their internal costs.

Maybe consider helping a workplace unionize and to push the union to decide upon open-sourcing the company's source code. That's what I hope to do.