This is an interesting question, because I'm also wondering where to PR my game xD
But I noticed the thing that over time different sites just add my game to themselves. It's very cool. It's worth just doing the game and the ads appear on their own.
Here on the forum among the developers also sometimes mutual PR. This can be the addition of some event in the game, taken from another game with the source (This is an example)
Not too long ago, one developer was collecting posters from everyone for a theater that he will have in the next update. He just scattered these posters on the walls and the player could look at it all (Poster is a render + game name). I also threw my poster in there, but I didn't check to see if it all worked out or not xD
By the way, here's my poster
Later, I was also inspired by this idea and created the same topic, only I didn't need posters for the theater, but pages for a magazine (a sexology textbook in general)
Guys sent me their posters and I added them to the game (Exactly as with the theater)
Well, that's how it is, maybe there are other interesting ways to PR, I do not know a lot about it. I'm just a novice developer.