No ads per se, but a recommendation tile and a kobo plus subscription tile on the main screen that just eats display space for nothing. I mainly use kobopatch to change the epub reader margins, get the page remaining in a chapter and block firmware updates and a few other details. Totally optional, it's just pure nitpicking here. Here is all my kobo modding work in this repo, you can also find what firmware mods are available...

https://github.com/obynio/kobopatch-config/tree/master/src

Thanks, I'm liking kobo more and more every time I read about it :).

Out of curiosity, why block updates? Does it conflict with your modification