Guys around the itch community say "itch doesn't support ads, you'll have to implement them yourself." That's okay, but how am I supposed to do that?

I mean,

• For Unity stuff, Unity Ads only supports mobile, not WebGL.
• For HTML stuff, Google Ads exists but I don't think that Google will approve ads that will only exist inside of an iframe that will exist on a domain that I don't even own. 
• Unity Answers/Forums and existent itch forum posts return no valuable information.

Has any of you implemented ads on browser games or tools on itch? Has anyone ever actually done that? If so, how? 

I like to make very small games and simple HTML tools. I don't want users to have to pay money to use them (much less have to download them), and nobody seems to click on the "Support this game" button. I'd like to just put one small non-intrusive banner on top to earn a bit from that work.

Any workaround ideas would be appreciated.