[zaarn]

I think the most basic and simple solution is to target ads not on the user but on the webpage and it's contents.

If the webpage is written in french (or visible as such) that reviews computer hardware, pick hardware ads first and if available in french. That is IMO a reasonable assumption to make and I don't believe that a lot of users will be mistargeted that hard.

Bigger publishers like newspapers could run ads depending on section, ie the politics section shows political ads and the weather section shows a raincoat ad.

The only downside I see is that localized ads don't work as well (ie, "local restaurant has cheap burgers" and "99+ women in <your area> want to talk to you on tinder!!!!"). Such places could put their ads on relevant pages though, ie the internet page of a local newspaper or the local communities' internet presence.