That sounds really promising. I am not familiar with the speech laws in Canada. Hopefully they are lenient enough for the type of content at stake.
It's not and never was a mater of speech laws. Patreon say nothing, create nothing and fund nothing. Technically and legally, they don't goes against any laws related to sexuality or pornography. The only legal issue is in the fact that they take benefit from illegals actions of others ; assuming that it's illegal to make incest games by example.
So, on the sole point of legality, what's needed is :
1) Video games are seen as fictional, like movies or books. It's not always the case, in Germany by example they are seen as toys ; it's why they can have swastika in movies but not in video games.
AND
2) Fictional depiction of an illegal act isn't an illegal act. Writing a book were the main character is a rapist isn't the same thing than being a rapist and so don't violate the laws against rape.
OR
3) Taking benefit of an illegal action isn't illegal if it wasn't your initial intend or if you were tricked to do it. It's the hardest part, especially because it can be legal in the site country but illegal in the creator country, or the opposite. Basically it mean that the site must be able to have a rule stating that creators promise to not goes against the law of their country, and it must be enough to legally argue that they were tricked and so have done nothing illegal.
As for the laws in Canada...
The
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basically state that it will be mostly illegal in Canada if it depict "undue exploitation of sex". This applying to any "written matter, picture, model, phonograph record or other thing whatever". So, games with incest, bestiality and/or none-consensual sex, whatever it's a 2D or 3D games, are illegals.
It's also illegal to "makes, prints, publishes, distributes,
circulates, sells,
exposes to public view" these games. This make a Canadian based adult version of Patreon in the obligation to ban incest, bestiality and none-consensual sex,
or at least force the creators to not put content on the site itself and not directly link to it. So, exactly like what we think is the position of Patreon actually.