Honestly, I always liked the idea for play2earn games to have some kind of "partnerships that bring in revenue" which make sense done in a way that is not annoying. This would help to make rewards more sustainable. I wouldn't mind a message to be added when a battle is over that shows 'extra rewards were provided by ..."

I wouldn't like just random popup adds. Anyway, the state the game is in right now with 95% of the activity just being bots fighting eachother and most players depressed by the game, I don't think anyone is jumping to use Splinterlands as a way to run ads.