Earlier in the year Corny Chat experimented with ads in the text chat area and room entry/login dialog. An ad would appear once every 15 minutes, unless you were paying any amount of sats via NWC. It had mixed results, and I decided to disable the feature until later.
I agree with you that there are meaningful ways to do ad supported systems and clients. ZBD, Fountain and Satograms was some of the first for this. The challenge is building ad systems that dont pull to many limited resources from client development, while remaining tasteful, and non overbearing. We dont want to recreate the old hellscape thats occured over the past 3 decades, yet we keep building clients that mimic the trad-tech and promote poor behaviors and outcomes.