Who said you have to promote it? Just tell the audience you released it there if they want it. I understand the silliness of this before you point it out. Yes, it's almost the same as only posting to Patreon, but it's not!
This goes to show me that you're hobbyist. OP is asking what is the better option for possible making this a career. And going the non-exclusive route won't bring you need cash flow unless you pay for advertisements.
If a readers options are, my work is free/going to be free then no one will find your book on Amazon to buy it. Exclusivity deal gives you more options but if your work isn't aimed at a popular genre then your book might fail. Going the patreon route is more for early work in progress and hopefully you build up enough of an audience to get readers become members.
But the is only so many people you could gain from SH, RR, and other sites before you plateau.
The best option is to have one good free novel that get you audience capture and create a second novel that you put on Amazon exclusively. You can always post in progress chapters on Patreon them take them down one the next volume is ready to be published on Amazon.
