I live within my means, avoiding the capitalist loop/profit printer of debt. I donate to a number of local charities working to feed, clothe, and house those in need. I volunteer my labor occasionally to various organizations. I advocate against car centric infrastructure and improved public transit in my local government. I offer free tech repairs to people, and if I have a needed part laying around I just provide it free. Before my car died I participated in a service to give people rides to the store or wherever.
No, I’m not changing the world, but I’m living my life in a sustainable way that I feel serves others and I find that fulfilling.