[redthrow]

I don't know about authors who themselves chose to publish with Big Tech or traditional publishers (& not asking for money elsewhere) but how about supporting authors who are asking for funding in crowdfunding sites (e.g. Indiegogo), membership subscription sites (e.g. Patreon), or the author's own website?

[yosito]

Yes, that's definitely an option. But I'd like to choose books for their content, not for their publisher.

[redthrow]

Well if the author you like chose Big Tech as their publisher, and you don't want to support Big Tech, and the author isn't asking for money in any other place, I don't know, maybe you can write a message to the author so you can give them money somehow (if the author is interested in it at all)?