Except that those communities are willing to pay for software.

Announce any "evil proprietary" software in places like HN, which should be about doing business to start with, and the top comments happen to be about forking, making FOSS clones and not paying a dime to evil overloards.

Qt being discussed here is a very good example, tons of comments on how not to pay Qt, switch to alternatives, and how much evil they are for wanting remuneration for their work.

Naturally companies then turn into the Apple, Google and Microsoft customer communities instead.

You are forgetting that so far qt is dual-licensed under GPL and commercial license so far. And there are a lot of FOSS projects that happen to use qt under the GPL so far. And for those projects there really is no other option than forking Qt or switching to alternatives if they stop providing the GPL licensed version for future version, since it would turn the FOSS project into a commercial one.

You are essentially arguing that making software available for Linux as well increases the probability of FOSS clones. I would argue the inverse, since the motivation to create a FOSS clone is much higher if such software doesn't exist at all for a given platform (since some people will just buy the software and be done with it).

My own experience is that trying to sell software to GNU/Linux customers is a lost battle, unless it is behind a server wall.

I've paid for plenty of GNU/Linux software. It has to be Free Software though, otherwise I'm not interested.

The confirmation that "evil proprietary business" companies should just focus on customers using Apple, Google and Microsoft platforms.

Thus giving the maximum possible motivation for people to develop their own (FOSS or not) clones/implementations. Bonus points for including actively hostile things like DRM or requiring license servers or hardware tokens to improve the user experience.