Some off-the-cuff ideas of how:
1. Make our own purchases "on principle", and hope that enough other techies do that, that economic pressure is applied to brands.
2. Make our own non-purchase technology adoptions "on principle".
3. Inform other techies, both on specifics of individual devices/architectures/vendors/etc., and to bring everyone up to speed on the basics (e.g., reasons for open standards, user-oriented products/services, avoiding lock-in, privacy-respecting, responsible security, etc.).
4. Inform non-techies, such as by pointing them at solutions in their interest, and in the interest of society.
5. Advise lawmakers, to complement whatever they're hearing from lobbyists.
6. Contribute code and other effort to open platforms, and actually use them.
7. Be careful about helping to prop up society-hostile platforms, such as by using them to the exclusion of something else, making them more palatable to the exclusion of something better, implicitly endorsing them, etc.
8. Keep principles a factor in who we go to work for, how we work while there, and whether we stay there.