In typical fashion I'm trying to define my terms before I get too deep into dissecting them.
In my view, an ethical technologist tries their best to use their work in tech to dismantle systems of oppression and injustice.
Oppression to me is power - earned and unearned, agreed or coerced and/or stolen - over people wielded in a cruel and unfair ways, and sometimes the existence of said power in the first place. Some power, say a parent over a child or a carer over a care receiver - can't be removed but can be used in unjust ways. Other power, such as that of a police officer over other citizens, is (yes, arguably) always unjust and should be abolished, dismantled, defunded, etc.
Injustice is any unfair treatment. I'm not sure it's possible to disentangle notions of fairness from power. Though some forms of unfair treatment can result where parties nominally have no power over each other, I think it's usually mediated by another party with more power, like with prejudiced hiring practices, unequal distribution of resources, etc. There's a study finding that those with relative amounts of power are more likely to notice and act when facing injustice towards themselves. This makes sense given they feel someone may listen or take action about their concerns on some level, whereas those with less power often have proof people will not.
I think people often think you have to be in the perfect, most ethical, most impactful role to start making a difference in matters of injustice and oppression. I would argue that whilst some roles are beyond the pale - must you work at the puppy smashing factory, making software shaving seconds off each individual smash? - I think most jobs have scope to be better, for their workers, for the world and for humanity at large. Even if the job itself shouldn't exist - either in a bullshit jobs fashion or in a "it's destroying the planet and the lives of people who are touched by it" way - the solidarity built around coming together with your coworkers to better the workplace and the lessons learnt from the challenges will be invaluable for the work of building a better world, or even just workplace, later down the line.
The idea of perfect action can hinder even the best intentioned person from actually doing anything positive. Making the path to better choices easier, be they in accessibility on the web for your companies website, pushing forth privacy concerns and security fixes for your users, or having the backs of your coworkers in workplace disputes all have their place as helpful actions. Trying to be ethical comes with the knowledge that producing or consuming anything comes with a cost as well as a benefit, and keeping that in mind as you move through the world is key to helping change it. It is not one perfect action that will change the world, but the consistent actions of many.